diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4bc3de4..a0f7132 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -26,18 +26,20 @@ set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
 endif()
 
 if(WIN32)
-list(APPEND CORE_EXTRA src/win32_largefilewrapper.c include/win32_largefilewrapper.h)
-elseif(APPLE OR GEKKO)
+list(APPEND CORE_EXTRA src/win32_largefilewrapper.c include/win32_largefilewrapper.h
+     src/athena/FileWriterWin32.cpp src/athena/FileReaderWin32.cpp)
+else()
+list(APPEND CORE_EXTRA src/athena/FileWriter.cpp src/athena/FileReader.cpp)
+if(APPLE OR GEKKO)
 list(APPEND CORE_EXTRA src/osx_largefilewrapper.c include/osx_largefilewrapper.h)
 if(GEKKO)
 list(APPEND CORE_EXTRA src/gekko_support.c include/gekko_support.h)
 endif()
 endif()
+endif()
 
 add_library(athena-core
     src/athena/Utility.cpp
-    src/athena/FileReader.cpp
-    src/athena/FileWriter.cpp
     src/athena/MemoryReader.cpp
     src/athena/MemoryWriter.cpp
     src/athena/Global.cpp
diff --git a/include/athena/FileReader.hpp b/include/athena/FileReader.hpp
index 70aa67b..932ce4d 100644
--- a/include/athena/FileReader.hpp
+++ b/include/athena/FileReader.hpp
@@ -1,9 +1,14 @@
 #ifndef FILESTREAM_HPP
 #define FILESTREAM_HPP
 
+#if _WIN32
+#include <windows.h>
+#else
+#include <stdio.h>
+#endif
+
 #include <string>
 #include <memory>
-#include <stdio.h>
 #include "athena/IStreamReader.hpp"
 
 namespace athena
@@ -38,7 +43,7 @@ public:
     void open();
     void close();
     inline bool isOpen() const
-    {return m_fileHandle != NULL;}
+    {return m_fileHandle != 0;}
     bool save();
     void seek(atInt64 pos, SeekOrigin origin = SeekOrigin::Current);
     atUint64 position() const;
@@ -46,14 +51,21 @@ public:
     atUint64 readUBytesToBuf(void* buf, atUint64 len);
 
     void setCacheSize(const atInt32 blockSize);
-    FILE* _fileHandle() {return m_fileHandle;}
+
+#if _WIN32
+    using HandleType = HANDLE;
+#else
+    using HandleType = FILE*;
+#endif
+
+    HandleType _fileHandle() {return m_fileHandle;}
 protected:
 #if _WIN32
     std::wstring m_filename;
 #else
     std::string  m_filename;
 #endif
-    FILE*        m_fileHandle;
+    HandleType   m_fileHandle;
     std::unique_ptr<atUint8[]>    m_cacheData;
     atInt32      m_blockSize;
     atInt32      m_curBlock;
diff --git a/include/athena/FileWriter.hpp b/include/athena/FileWriter.hpp
index f1222c7..41ac8d0 100644
--- a/include/athena/FileWriter.hpp
+++ b/include/athena/FileWriter.hpp
@@ -1,8 +1,12 @@
 #ifndef FILEWRITER_HPP
 #define FILEWRITER_HPP
 
-#include "athena/IStreamWriter.hpp"
+#if _WIN32
+#include <windows.h>
+#else
 #include <stdio.h>
+#endif
+#include "athena/IStreamWriter.hpp"
 
 namespace athena
 {
@@ -35,20 +39,26 @@ public:
     void open(bool overwrite = true);
     void close();
     inline bool isOpen() const
-    {return m_fileHandle != NULL;}
+    {return m_fileHandle != 0;}
     void seek(atInt64 pos, SeekOrigin origin = SeekOrigin::Current);
     atUint64 position() const;
     atUint64 length() const;
     void writeUBytes(const atUint8* data, atUint64 len);
 
-    FILE* _fileHandle() {return m_fileHandle;}
+#if _WIN32
+    using HandleType = HANDLE;
+#else
+    using HandleType = FILE*;
+#endif
+
+    HandleType _fileHandle() {return m_fileHandle;}
 private:
 #if _WIN32
     std::wstring m_filename;
 #else
     std::string  m_filename;
 #endif
-    FILE*        m_fileHandle;
+    HandleType   m_fileHandle;
     atUint8      m_currentByte;
     atUint64     m_bytePosition;
     bool         m_globalErr;
diff --git a/src/athena/FileReader.cpp b/src/athena/FileReader.cpp
index c6459f4..9aeefed 100644
--- a/src/athena/FileReader.cpp
+++ b/src/athena/FileReader.cpp
@@ -1,8 +1,6 @@
 #include "athena/FileReader.hpp"
 
-#if _WIN32
-#include "win32_largefilewrapper.h"
-#elif __APPLE__
+#if __APPLE__
 #include "osx_largefilewrapper.h"
 #elif GEKKO
 #include "gekko_support.h"
@@ -19,11 +17,7 @@ FileReader::FileReader(const std::string& filename, atInt32 cacheSize, bool glob
       m_offset(0),
       m_globalErr(globalErr)
 {
-#if _WIN32
-    m_filename = utility::utf8ToWide(filename);
-#else
     m_filename = filename;
-#endif
     open();
     setCacheSize(cacheSize);
 }
@@ -34,11 +28,7 @@ FileReader::FileReader(const std::wstring& filename, atInt32 cacheSize, bool glo
       m_offset(0),
       m_globalErr(globalErr)
 {
-#if _WIN32
-    m_filename = filename;
-#else
     m_filename = utility::wideToUtf8(filename);
-#endif
     open();
     setCacheSize(cacheSize);
 }
@@ -51,11 +41,7 @@ FileReader::~FileReader()
 
 void FileReader::open()
 {
-#if _WIN32
-    m_fileHandle = _wfopen(m_filename.c_str(), L"rb");
-#else
     m_fileHandle = fopen(m_filename.c_str(), "rb");
-#endif
 
     if (!m_fileHandle)
     {
@@ -197,7 +183,7 @@ atUint64 FileReader::readUBytesToBuf(void* buf, atUint64 len)
             if (cacheSize + cacheOffset > m_blockSize)
                 cacheSize = m_blockSize - cacheOffset;
 
-            memcpy(dst, m_cacheData.get() + cacheOffset, cacheSize);
+            memmove(dst, m_cacheData.get() + cacheOffset, cacheSize);
             dst += cacheSize;
             rem -= cacheSize;
             cacheOffset = 0;
diff --git a/src/athena/FileReaderWin32.cpp b/src/athena/FileReaderWin32.cpp
new file mode 100644
index 0000000..252cca8
--- /dev/null
+++ b/src/athena/FileReaderWin32.cpp
@@ -0,0 +1,227 @@
+#include "athena/FileReader.hpp"
+#include "win32_largefilewrapper.h"
+
+namespace athena
+{
+namespace io
+{
+FileReader::FileReader(const std::string& filename, atInt32 cacheSize, bool globalErr)
+    : m_fileHandle(nullptr),
+      m_cacheData(nullptr),
+      m_offset(0),
+      m_globalErr(globalErr)
+{
+    m_filename = utility::utf8ToWide(filename);
+    open();
+    setCacheSize(cacheSize);
+}
+
+FileReader::FileReader(const std::wstring& filename, atInt32 cacheSize, bool globalErr)
+    : m_fileHandle(nullptr),
+      m_cacheData(nullptr),
+      m_offset(0),
+      m_globalErr(globalErr)
+{
+    m_filename = filename;
+    open();
+    setCacheSize(cacheSize);
+}
+
+FileReader::~FileReader()
+{
+    if (isOpen())
+        close();
+}
+
+void FileReader::open()
+{
+    m_fileHandle = CreateFileW(m_filename.c_str(), GENERIC_READ, FILE_SHARE_READ,
+                               nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+
+    if (m_fileHandle == INVALID_HANDLE_VALUE)
+    {
+        m_fileHandle = 0;
+        std::string _filename = filename();
+        if (m_globalErr)
+            atError("File not found '%s'", _filename.c_str());
+        setError();
+        return;
+    }
+
+    // reset error
+    m_hasError = false;
+}
+
+void FileReader::close()
+{
+    if (!m_fileHandle)
+    {
+        if (m_globalErr)
+            atError("Cannot close an unopened stream");
+        setError();
+        return;
+    }
+
+    CloseHandle(m_fileHandle);
+    m_fileHandle = 0;
+    return;
+}
+
+void FileReader::seek(atInt64 pos, SeekOrigin origin)
+{
+    if (!isOpen())
+        return;
+
+    // check block position
+    if (m_blockSize > 0)
+    {
+        atUint64 oldOff = m_offset;
+        switch(origin)
+        {
+        case SeekOrigin::Begin:
+            m_offset = pos;
+            break;
+        case SeekOrigin::Current:
+            m_offset += pos;
+            break;
+        case SeekOrigin::End:
+            m_offset = length() - pos;
+            break;
+        }
+        if (m_offset > length())
+        {
+            oldOff = m_offset;
+            if (m_globalErr)
+                atError("Unable to seek in file");
+            setError();
+            return;
+        }
+
+        size_t block = m_offset / m_blockSize;
+        if (block != m_curBlock)
+        {
+            LARGE_INTEGER li;
+            li.QuadPart = block * m_blockSize;
+            SetFilePointerEx(m_fileHandle, li, nullptr, FILE_BEGIN);
+            ReadFile(m_fileHandle, m_cacheData.get(), m_blockSize, nullptr, nullptr);
+            m_curBlock = (atInt32)block;
+        }
+    }
+    else
+    {
+        LARGE_INTEGER li;
+        li.QuadPart = pos;
+        if (!SetFilePointerEx(m_fileHandle, li, nullptr, DWORD(origin)))
+        {
+            if (m_globalErr)
+                atError("Unable to seek in file");
+            setError();
+        }
+    }
+}
+
+atUint64 FileReader::position() const
+{
+    if (!isOpen())
+    {
+        if (m_globalErr)
+            atError("File not open");
+        return 0;
+    }
+
+    if (m_blockSize > 0)
+        return m_offset;
+    else
+    {
+        LARGE_INTEGER li = {};
+        LARGE_INTEGER res;
+        SetFilePointerEx(m_fileHandle, li, &res, FILE_CURRENT);
+        return res.QuadPart;
+    }
+}
+
+atUint64 FileReader::length() const
+{
+    if (!isOpen())
+    {
+        if (m_globalErr)
+            atError("File not open");
+        return 0;
+    }
+
+    LARGE_INTEGER res;
+    GetFileSizeEx(m_fileHandle, &res);
+    return res.QuadPart;
+}
+
+atUint64 FileReader::readUBytesToBuf(void* buf, atUint64 len)
+{
+    if (!isOpen())
+    {
+        if (m_globalErr)
+            atError("File not open for reading");
+        setError();
+        return 0;
+    }
+
+    if (m_blockSize <= 0)
+    {
+        DWORD ret = 0;
+        ReadFile(m_fileHandle, buf, len, &ret, nullptr);
+        return ret;
+    }
+    else
+    {
+        LARGE_INTEGER fs;
+        GetFileSizeEx(m_fileHandle, &fs);
+        if (m_offset >= fs.QuadPart)
+            return 0;
+        if (m_offset + len >= fs.QuadPart)
+            len = fs.QuadPart - m_offset;
+
+        size_t block = m_offset / m_blockSize;
+        atUint64 cacheOffset = m_offset % m_blockSize;
+        atUint64 cacheSize;
+        atUint64 rem = len;
+        atUint8* dst = (atUint8*)buf;
+
+        while (rem)
+        {
+            if (block != m_curBlock)
+            {
+                LARGE_INTEGER li;
+                li.QuadPart = block * m_blockSize;
+                SetFilePointerEx(m_fileHandle, li, nullptr, FILE_BEGIN);
+                ReadFile(m_fileHandle, m_cacheData.get(), m_blockSize, nullptr, nullptr);
+                m_curBlock = (atInt32)block;
+            }
+
+            cacheSize = rem;
+            if (cacheSize + cacheOffset > m_blockSize)
+                cacheSize = m_blockSize - cacheOffset;
+
+            memmove(dst, m_cacheData.get() + cacheOffset, cacheSize);
+            dst += cacheSize;
+            rem -= cacheSize;
+            cacheOffset = 0;
+            ++block;
+        }
+        m_offset += len;
+        return dst - (atUint8*)buf;
+    }
+}
+
+void FileReader::setCacheSize(const atInt32 blockSize)
+{
+    m_blockSize = blockSize;
+
+    if (m_blockSize > length())
+        m_blockSize = (atInt32)length();
+
+    m_curBlock = -1;
+    if (m_blockSize > 0)
+        m_cacheData.reset(new atUint8[m_blockSize]);
+}
+
+} // io
+} // Athena
diff --git a/src/athena/FileWriter.cpp b/src/athena/FileWriter.cpp
index 484059f..77215c9 100644
--- a/src/athena/FileWriter.cpp
+++ b/src/athena/FileWriter.cpp
@@ -1,8 +1,6 @@
 #include "athena/FileWriter.hpp"
 
-#if _WIN32
-#include "win32_largefilewrapper.h"
-#elif __APPLE__
+#if __APPLE__
 #include "osx_largefilewrapper.h"
 #elif GEKKO
 #include "gekko_support.h"
@@ -18,11 +16,7 @@ FileWriter::FileWriter(const std::string& filename, bool overwrite, bool globalE
       m_bytePosition(0),
       m_globalErr(globalErr)
 {
-#if _WIN32
-    m_filename = utility::utf8ToWide(filename);
-#else
     m_filename = filename;
-#endif
     open(overwrite);
 }
 
@@ -31,11 +25,7 @@ FileWriter::FileWriter(const std::wstring& filename, bool overwrite, bool global
       m_bytePosition(0),
       m_globalErr(globalErr)
 {
-#if _WIN32
-    m_filename = filename;
-#else
     m_filename = utility::wideToUtf8(filename);
-#endif
     open(overwrite);
 }
 
@@ -47,19 +37,6 @@ FileWriter::~FileWriter()
 
 void FileWriter::open(bool overwrite)
 {
-#if _WIN32
-    if (overwrite)
-        m_fileHandle = _wfopen(m_filename.c_str(), L"w+b");
-    else
-    {
-        m_fileHandle = _wfopen(m_filename.c_str(), L"r+b");
-        if (m_fileHandle)
-        {
-            fclose(m_fileHandle);
-            m_fileHandle = _wfopen(m_filename.c_str(), L"r+b");
-        }
-    }
-#else
     if (overwrite)
         m_fileHandle = fopen(m_filename.c_str(), "w+b");
     else
@@ -71,7 +48,6 @@ void FileWriter::open(bool overwrite)
             m_fileHandle = fopen(m_filename.c_str(), "r+b");
         }
     }
-#endif
 
     if (!m_fileHandle)
     {
@@ -97,7 +73,6 @@ void FileWriter::close()
 
     fclose(m_fileHandle);
     m_fileHandle = NULL;
-    return;
 }
 
 void FileWriter::seek(atInt64 pos, SeekOrigin origin)
diff --git a/src/athena/FileWriterWin32.cpp b/src/athena/FileWriterWin32.cpp
new file mode 100644
index 0000000..198d796
--- /dev/null
+++ b/src/athena/FileWriterWin32.cpp
@@ -0,0 +1,126 @@
+#include "athena/FileWriter.hpp"
+#include "win32_largefilewrapper.h"
+
+namespace athena
+{
+namespace io
+{
+FileWriter::FileWriter(const std::string& filename, bool overwrite, bool globalErr)
+    : m_fileHandle(0),
+      m_bytePosition(0),
+      m_globalErr(globalErr)
+{
+    m_filename = utility::utf8ToWide(filename);
+    open(overwrite);
+}
+
+FileWriter::FileWriter(const std::wstring& filename, bool overwrite, bool globalErr)
+    : m_fileHandle(0),
+      m_bytePosition(0),
+      m_globalErr(globalErr)
+{
+    m_filename = filename;
+    open(overwrite);
+}
+
+FileWriter::~FileWriter()
+{
+    if (isOpen())
+        close();
+}
+
+void FileWriter::open(bool overwrite)
+{
+    if (overwrite)
+    {
+        m_fileHandle = CreateFileW(m_filename.c_str(), GENERIC_WRITE, FILE_SHARE_WRITE,
+                                   nullptr, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, nullptr);
+    }
+    else
+    {
+        m_fileHandle = CreateFileW(m_filename.c_str(), GENERIC_WRITE, FILE_SHARE_WRITE,
+                                   nullptr, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, nullptr);
+    }
+
+    if (m_fileHandle == INVALID_HANDLE_VALUE)
+    {
+        m_fileHandle = 0;
+        if (m_globalErr)
+            atError("Unable to open file '%s'", filename().c_str());
+        setError();
+        return;
+    }
+
+    // reset error
+    m_hasError = false;
+}
+
+void FileWriter::close()
+{
+    if (!m_fileHandle)
+    {
+        if (m_globalErr)
+            atError("Cannot close an unopened stream");
+        setError();
+        return;
+    }
+
+    CloseHandle(m_fileHandle);
+    m_fileHandle = 0;
+}
+
+void FileWriter::seek(atInt64 pos, SeekOrigin origin)
+{
+    if (!isOpen())
+    {
+        if (m_globalErr)
+            atError("Unable to seek in file, not open");
+        setError();
+        return;
+    }
+
+    LARGE_INTEGER li;
+    li.QuadPart = pos;
+    if (!SetFilePointerEx(m_fileHandle, li, nullptr, DWORD(origin)))
+    {
+        if (m_globalErr)
+            atError("Unable to seek in file");
+        setError();
+    }
+}
+
+atUint64 FileWriter::position() const
+{
+    LARGE_INTEGER li = {};
+    LARGE_INTEGER res;
+    SetFilePointerEx(m_fileHandle, li, &res, FILE_CURRENT);
+    return res.QuadPart;
+}
+
+atUint64 FileWriter::length() const
+{
+    return utility::fileSize(m_filename);
+}
+
+void FileWriter::writeUBytes(const atUint8* data, atUint64 len)
+{
+    if (!isOpen())
+    {
+        if (m_globalErr)
+            atError("File not open for writing");
+        setError();
+        return;
+    }
+
+    DWORD ret = 0;
+    WriteFile(m_fileHandle, data, len, &ret, nullptr);
+    if (ret != len)
+    {
+        if (m_globalErr)
+            atError("Unable to write to stream");
+        setError();
+    }
+}
+
+}
+} // Athena
diff --git a/src/athena/MemoryReader.cpp b/src/athena/MemoryReader.cpp
index 0d60548..d642ab8 100644
--- a/src/athena/MemoryReader.cpp
+++ b/src/athena/MemoryReader.cpp
@@ -65,7 +65,7 @@ MemoryCopyReader::MemoryCopyReader(const void* data, atUint64 length)
 
     m_dataCopy.reset(new atUint8[m_length]);
     m_data = m_dataCopy.get();
-    memcpy(m_dataCopy.get(), data, m_length);
+    memmove(m_dataCopy.get(), data, m_length);
 }
 
 void MemoryReader::seek(atInt64 position, SeekOrigin origin)
@@ -127,7 +127,7 @@ void MemoryCopyReader::setData(const atUint8* data, atUint64 length)
 {
     m_dataCopy.reset(new atUint8[length]);
     m_data = m_dataCopy.get();
-    memcpy(m_dataCopy.get(), data, length);
+    memmove(m_dataCopy.get(), data, length);
     m_length = length;
     m_position = 0;
 }
@@ -136,7 +136,7 @@ atUint8* MemoryReader::data() const
 {
     atUint8* ret = new atUint8[m_length];
     memset(ret, 0, m_length);
-    memcpy(ret, m_data, m_length);
+    memmove(ret, m_data, m_length);
     return ret;
 }
 
@@ -151,7 +151,7 @@ atUint64 MemoryReader::readUBytesToBuf(void* buf, atUint64 length)
         return 0;
     }
 
-    memcpy(buf, reinterpret_cast<const atUint8*>(m_data) + m_position, length);
+    memmove(buf, reinterpret_cast<const atUint8*>(m_data) + m_position, length);
     m_position += length;
     return length;
 }
diff --git a/src/athena/MemoryWriter.cpp b/src/athena/MemoryWriter.cpp
index a3df929..7b7cd66 100644
--- a/src/athena/MemoryWriter.cpp
+++ b/src/athena/MemoryWriter.cpp
@@ -59,7 +59,7 @@ MemoryCopyWriter::MemoryCopyWriter(atUint8* data, atUint64 length)
     m_dataCopy.reset(new atUint8[length]);
     m_data = m_dataCopy.get();
     if (data)
-        memcpy(m_data, data, length);
+        memmove(m_data, data, length);
 }
 
 MemoryCopyWriter::MemoryCopyWriter(const std::string& filename)
@@ -202,7 +202,7 @@ void MemoryCopyWriter::setData(const atUint8* data, atUint64 length)
 {
     m_dataCopy.reset(new atUint8[length]);
     m_data = m_dataCopy.get();
-    memcpy(m_data, data, length);
+    memmove(m_data, data, length);
     m_length = length;
     m_position = 0;
     m_bufferOwned = false;
@@ -212,7 +212,7 @@ atUint8* MemoryWriter::data() const
 {
     atUint8* ret = new atUint8[m_length];
     memset(ret, 0, m_length);
-    memcpy(ret, m_data, m_length);
+    memmove(ret, m_data, m_length);
     return ret;
 }
 
@@ -280,7 +280,7 @@ void MemoryWriter::writeUBytes(const atUint8* data, atUint64 length)
         return;
     }
 
-    memcpy(reinterpret_cast<atInt8*>(m_data + m_position), data, length);
+    memmove(reinterpret_cast<atInt8*>(m_data + m_position), data, length);
 
     m_position += length;
 }
@@ -297,7 +297,7 @@ void MemoryCopyWriter::writeUBytes(const atUint8* data, atUint64 length)
     if (m_position + length > m_length)
         resize(m_position + length);
 
-    memcpy(reinterpret_cast<atInt8*>(m_data + m_position), data, length);
+    memmove(reinterpret_cast<atInt8*>(m_data + m_position), data, length);
 
     m_position += length;
 }
@@ -315,7 +315,7 @@ void MemoryCopyWriter::resize(atUint64 newSize)
     memset(newArray, 0, newSize);
 
     if (m_dataCopy)
-        memcpy(newArray, m_dataCopy.get(), m_length);
+        memmove(newArray, m_dataCopy.get(), m_length);
     m_dataCopy.reset(newArray);
 
     // Swap the pointer and size out for the new ones.
diff --git a/src/sha1.cpp b/src/sha1.cpp
index 6bb81ed..5ad04b1 100644
--- a/src/sha1.cpp
+++ b/src/sha1.cpp
@@ -395,7 +395,7 @@ atUint8* getSha1(atUint8* stuff, atUint32 stuff_size)
         if (!athena::utility::isSystemBigEndian())
             val = athena::utility::swap32(val);
 
-        memcpy((char*)ret + (i * 4), &val, 4);
+        memmove((char*)ret + (i * 4), &val, 4);
     }
 
     return ret;