diff --git a/src/files.cpp b/src/files.cpp
index d7dfc2cbe7..981b351a99 100644
--- a/src/files.cpp
+++ b/src/files.cpp
@@ -33,11 +33,15 @@
 **
 */
 
+#define USE_WINDOWS_DWORD
+#include "LzmaDec.h"
+
 #include "files.h"
 #include "i_system.h"
 #include "templates.h"
 #include "m_misc.h"
 
+
 //==========================================================================
 //
 // FileReader
@@ -370,6 +374,15 @@ extern "C" void bz_internal_error (int errcode)
 //
 //==========================================================================
 
+// This is retarded but necessary to work around the inclusion of windows.h in recent
+// LZMA versions, meaning it's no longer possible to include the LZMA headers in files.h. 
+// As a result we cannot declare the CLzmaDec member in the header so we work around
+// it my wrapping it into another struct that can be declared anonymously in the header.
+struct FileReaderLZMA::StreamPointer
+{
+	CLzmaDec Stream;
+};
+
 static void *SzAlloc(void *, size_t size) { return malloc(size); }
 static void SzFree(void *, void *address) { free(address); }
 ISzAlloc g_Alloc = { SzAlloc, SzFree };
@@ -398,20 +411,22 @@ FileReaderLZMA::FileReaderLZMA (FileReader &file, size_t uncompressed_size, bool
 
 	FillBuffer();
 
-	LzmaDec_Construct(&Stream);
-	err = LzmaDec_Allocate(&Stream, header + 4, LZMA_PROPS_SIZE, &g_Alloc);
+	Streamp = new StreamPointer;
+	LzmaDec_Construct(&Streamp->Stream);
+	err = LzmaDec_Allocate(&Streamp->Stream, header + 4, LZMA_PROPS_SIZE, &g_Alloc);
 
 	if (err != SZ_OK)
 	{
 		I_Error("FileReaderLZMA: LzmaDec_Allocate failed: %d\n", err);
 	}
 
-	LzmaDec_Init(&Stream);
+	LzmaDec_Init(&Streamp->Stream);
 }
 
 FileReaderLZMA::~FileReaderLZMA ()
 {
-	LzmaDec_Free(&Stream, &g_Alloc);
+	LzmaDec_Free(&Streamp->Stream, &g_Alloc);
+	delete Streamp;
 }
 
 long FileReaderLZMA::Read (void *buffer, long len)
@@ -426,7 +441,7 @@ long FileReaderLZMA::Read (void *buffer, long len)
 		size_t out_processed = len;
 		size_t in_processed = InSize;
 
-		err = LzmaDec_DecodeToBuf(&Stream, next_out, &out_processed, InBuff + InPos, &in_processed, finish_mode, &status);
+		err = LzmaDec_DecodeToBuf(&Streamp->Stream, next_out, &out_processed, InBuff + InPos, &in_processed, finish_mode, &status);
 		InPos += in_processed;
 		InSize -= in_processed;
 		next_out += out_processed;
diff --git a/src/files.h b/src/files.h
index ebe9665a44..f7d061c8e5 100644
--- a/src/files.h
+++ b/src/files.h
@@ -4,7 +4,6 @@
 #include <stdio.h>
 #include <zlib.h>
 #include "bzlib.h"
-#include "LzmaDec.h"
 #include "doomtype.h"
 #include "m_swap.h"
 
@@ -257,6 +256,8 @@ private:
 // Wraps around a FileReader to decompress a lzma stream
 class FileReaderLZMA : public FileReaderBase
 {
+	struct StreamPointer;
+
 public:
 	FileReaderLZMA (FileReader &file, size_t uncompressed_size, bool zip);
 	~FileReaderLZMA ();
@@ -308,7 +309,7 @@ private:
 
 	FileReader &File;
 	bool SawEOF;
-	CLzmaDec Stream;
+	StreamPointer *Streamp;	// anonymous pointer to LKZA decoder struct - to avoid including the LZMA headers globally
 	size_t Size;
 	size_t InPos, InSize;
 	size_t OutProcessed;
diff --git a/src/resourcefiles/file_7z.cpp b/src/resourcefiles/file_7z.cpp
index 53653bb59e..c3845d8cc6 100644
--- a/src/resourcefiles/file_7z.cpp
+++ b/src/resourcefiles/file_7z.cpp
@@ -32,6 +32,10 @@
 **
 **
 */
+#define USE_WINDOWS_DWORD
+
+#include "7z.h"
+#include "7zCrc.h"
 
 #include "resourcefile.h"
 #include "cmdlib.h"
@@ -41,8 +45,6 @@
 #include "i_system.h"
 #include "w_wad.h"
 
-#include "7z.h"
-#include "7zCrc.h"
 
 
 //-----------------------------------------------------------------------
diff --git a/tools/zipdir/zipdir.c b/tools/zipdir/zipdir.c
index 9b521bedf3..1479952e09 100644
--- a/tools/zipdir/zipdir.c
+++ b/tools/zipdir/zipdir.c
@@ -129,7 +129,7 @@ typedef struct compressor_s
 	int method;
 } compressor_t;
 
-typedef unsigned int DWORD;
+typedef unsigned int UINT32;
 typedef unsigned short WORD;
 typedef unsigned char BYTE;
 
@@ -139,49 +139,49 @@ typedef unsigned char BYTE;
 //#pragma pack(push,1)
 typedef struct
 {
-	DWORD	Magic;						// 0
+	UINT32	Magic;						// 0
 	BYTE	VersionToExtract[2];		// 4
 	WORD	Flags;						// 6
 	WORD	Method;						// 8
 	WORD	ModTime;					// 10
 	WORD	ModDate;					// 12
-	DWORD	CRC32;						// 14
-	DWORD	CompressedSize;				// 18
-	DWORD	UncompressedSize;			// 22
+	UINT32	CRC32;						// 14
+	UINT32	CompressedSize;				// 18
+	UINT32	UncompressedSize;			// 22
 	WORD	NameLength;					// 26
 	WORD	ExtraLength;				// 28
 } LocalFileHeader;
 
 typedef struct
 {
-	DWORD	Magic;
+	UINT32	Magic;
 	BYTE	VersionMadeBy[2];
 	BYTE	VersionToExtract[2];
 	WORD	Flags;
 	WORD	Method;
 	WORD	ModTime;
 	WORD	ModDate;
-	DWORD	CRC32;
-	DWORD	CompressedSize;
-	DWORD	UncompressedSize;
+	UINT32	CRC32;
+	UINT32	CompressedSize;
+	UINT32	UncompressedSize;
 	WORD	NameLength;
 	WORD	ExtraLength;
 	WORD	CommentLength;
 	WORD	StartingDiskNumber;
 	WORD	InternalAttributes;
-	DWORD	ExternalAttributes;
-	DWORD	LocalHeaderOffset;
+	UINT32	ExternalAttributes;
+	UINT32	LocalHeaderOffset;
 } CentralDirectoryEntry;
 
 typedef struct
 {
-	DWORD	Magic;
+	UINT32	Magic;
 	WORD	DiskNumber;
 	WORD	FirstDisk;
 	WORD	NumEntries;
 	WORD	NumEntriesOnAllDisks;
-	DWORD	DirectorySize;
-	DWORD	DirectoryOffset;
+	UINT32	DirectorySize;
+	UINT32	DirectoryOffset;
 	WORD	ZipCommentLength;
 } EndOfCentralDirectory;
 //#pragma pack(pop)
@@ -1373,7 +1373,7 @@ BYTE *find_central_dir(FILE *fin)
 	back_read = 4;
 	while (back_read < max_back)
 	{
-		DWORD read_size, read_pos;
+		UINT32 read_size, read_pos;
 		int i;
 		if (back_read + BUFREADCOMMENT > max_back) 
 			back_read = max_back;
@@ -1420,12 +1420,12 @@ BYTE *find_central_dir(FILE *fin)
 		free(dir);
 		return NULL;
 	}
-	if (*(DWORD *)dir != ZIP_CENTRALFILE)
+	if (*(UINT32 *)dir != ZIP_CENTRALFILE)
 	{
 		free(dir);
 		return NULL;
 	}
-	*(DWORD *)(dir + LittleLong(eod.DirectorySize)) = ZIP_ENDOFDIR;
+	*(UINT32 *)(dir + LittleLong(eod.DirectorySize)) = ZIP_ENDOFDIR;
 	return dir;
 }
 
@@ -1444,7 +1444,7 @@ CentralDirectoryEntry *find_file_in_zip(BYTE *dir, const char *path, unsigned in
 	CentralDirectoryEntry *ent;
 	int flags;
 
-	while (*(DWORD *)dir == ZIP_CENTRALFILE)
+	while (*(UINT32 *)dir == ZIP_CENTRALFILE)
 	{
 		ent = (CentralDirectoryEntry *)dir;
 		if (pathlen == LittleShort(ent->NameLength) &&
@@ -1455,7 +1455,7 @@ CentralDirectoryEntry *find_file_in_zip(BYTE *dir, const char *path, unsigned in
 		}
 		dir += sizeof(*ent) + LittleShort(ent->NameLength) + LittleShort(ent->ExtraLength) + LittleShort(ent->CommentLength);
 	}
-	if (*(DWORD *)dir != ZIP_CENTRALFILE)
+	if (*(UINT32 *)dir != ZIP_CENTRALFILE)
 	{
 		return NULL;
 	}
@@ -1495,7 +1495,7 @@ int copy_zip_file(FILE *zip, file_entry_t *file, FILE *ozip, CentralDirectoryEnt
 {
 	LocalFileHeader lfh;
 	BYTE *buf;
-	DWORD buf_size;
+	UINT32 buf_size;
 
 	if (fseek(ozip, LittleLong(ent->LocalHeaderOffset), SEEK_SET) != 0)
 	{