diff --git a/saco/filechecks.cpp b/saco/filechecks.cpp
new file mode 100644
index 0000000..65078a4
--- /dev/null
+++ b/saco/filechecks.cpp
@@ -0,0 +1,128 @@
+
+#include <windows.h>
+#include "filechecks.h"
+#include "filehooks.h"
+#include "../saco/filesystem.h"
+#include "../saco/archive/archivefs.h"	// The new FileSystem
+#include "md5.h"
+
+extern CFileSystem *pFileSystem;
+
+DWORD WINAPI Arch_SetFilePointer( HANDLE hFile,LONG lDistanceToMove,
+								  PLONG lpDistanceToMoveHigh,DWORD dwMoveMethod );
+BOOL WINAPI Arch_ReadFile( HANDLE hFile,LPVOID lpBuffer,
+						   DWORD nNumberOfBytesToRead,
+						   LPDWORD lpNumberOfBytesRead,
+						   LPOVERLAPPED lpOverlapped );
+
+BOOL IsCheckableFile(CHAR* szExt)
+{
+	// Obfuscate the code in the dll slightly to make tracing it harder
+	// very hard coded and messy but should detect ide and ipl case insensitively
+	if ((*szExt++ & 0xDF) != 'I') return FALSE;
+	if ((*szExt | 0x20) + 7 != 'k')
+	{
+		if ((*szExt & 0xDF) - 17 == '?')
+		{
+			szExt++;
+			if (((*szExt | 0x20) - 'k') == 1) return TRUE;
+		}
+	}
+	else
+	{
+		if (((*++szExt & 0xDF) - 'E')) return FALSE;
+		return TRUE;
+	}
+
+	return FALSE;
+}
+
+void CheckFileHash(int dwFileHash, HANDLE hFile)
+{
+	DWORD dwFileIndex = ((CArchiveFS*)pFileSystem)->GetFileIndex(0xa848b69a);
+
+	if (dwFileIndex != FS_INVALID_FILE)
+	{
+		BYTE *pbData = pFileSystem->GetFileData(dwFileIndex);
+		BYTE byteCount = *pbData++; // Get and jump over header
+
+		// Search the tree
+		BOOL bFound = FALSE;
+		BYTE i = 0;
+		BINARY_TREE* pItem;
+
+		while(!bFound && i < byteCount)
+		{
+			pItem = (BINARY_TREE*)(pbData + (i * sizeof (BINARY_TREE)));
+			if (pItem->dwFileHash == dwFileHash)
+			{
+				i = pItem->byteData;
+				bFound = TRUE;
+			}
+			else if (pItem->dwFileHash < dwFileHash)
+			{
+				i = pItem->byteRight;
+			}
+			else
+			{
+				i = pItem->byteLeft;
+			}
+		}
+#ifndef _DEBUG
+		if (i >= byteCount)
+		{
+			return;
+		}
+#endif
+
+		// Jump over the header and tree blocks into the data block
+		MD5_DATA* mdHash = (MD5_DATA*)(pbData + (byteCount * sizeof (BINARY_TREE)) + (i * sizeof (MD5_DATA)));
+
+		DWORD dwWasRead;
+		BYTE szBuffer[1024];
+
+		MD5_CTX mdCTX;
+		MD5Init(&mdCTX);
+		DWORD dwDataToRead = 1024;
+
+		while (Arch_ReadFile(hFile, (LPVOID)szBuffer, dwDataToRead, &dwWasRead, NULL) && dwWasRead)
+		{
+			MD5Update(&mdCTX, szBuffer, dwWasRead);
+		}
+
+		BYTE byteDigest[16];
+		MD5Final(byteDigest, &mdCTX);
+
+		LONG lDistanceHigh = 0;
+		Arch_SetFilePointer(hFile, 0, &lDistanceHigh, FILE_BEGIN);
+
+		for (i = 0; i < 16; i++)
+		{
+			if ((BYTE)byteDigest[i] != (BYTE)mdHash->byteData[i])
+			{
+#ifndef _DEBUG
+				break;
+#endif
+			}
+		}
+	}
+}
+
+int GetFileNameHash(char* szFileName)
+{
+	// Based on a Jenkins hash
+	int dwHash = 0;
+	char* len = strlen(szFileName) + szFileName;
+	while (szFileName < len)
+	{
+		char c = *szFileName;
+		dwHash += (c > 'Z' || c < 'A') ? (c) : (c | 0x20); // Lower case
+		dwHash += (dwHash << 10);
+		dwHash ^= (dwHash >> 6);
+		szFileName++;
+	}
+	dwHash += (dwHash << 3);
+	dwHash ^= (dwHash >> 11);
+	dwHash += (dwHash << 15);
+	return dwHash;
+}
diff --git a/saco/filechecks.h b/saco/filechecks.h
new file mode 100644
index 0000000..d4989c9
--- /dev/null
+++ b/saco/filechecks.h
@@ -0,0 +1,18 @@
+
+typedef struct _BIN_TREE
+{
+	int dwFileHash;
+	BYTE byteLeft;
+	BYTE byteRight;
+	BYTE byteData;
+	BYTE bytePadding;
+} BINARY_TREE;
+
+typedef struct _MD5_DATA
+{
+	BYTE byteData[16];
+} MD5_DATA;
+
+BOOL IsCheckableFile(CHAR* szExt);
+void CheckFileHash(int dwFileHash, HANDLE hFile);
+int GetFileNameHash(char* szFileName);
diff --git a/saco/saco.vcproj b/saco/saco.vcproj
index d5edd06..6071f27 100644
--- a/saco/saco.vcproj
+++ b/saco/saco.vcproj
@@ -703,6 +703,12 @@
 		<File
 			RelativePath=".\fhicl-sha1.h">
 		</File>
+		<File
+			RelativePath=".\filechecks.cpp">
+		</File>
+		<File
+			RelativePath=".\filechecks.h">
+		</File>
 		<File
 			RelativePath=".\filehooks.cpp">
 		</File>