Things I had to do when migrating from MS VS 2003 project file to MS VS 2005 project file:

added '/D "_CRT_SECURE_NO_DEPRECATE"' to compiler switches
added #ifndef around some macro definitions that caused 'already defined' precompiler errors
added #ifndef and fixed newlines around some #define in image.c (newlines were broken and it messed with the rest of the code in that file)
removed asm (.s) files from project file
replaced unlink() with _unlink() and getcwd() with _getcwd
removed libcmt ignored default libraries, added MSVCRT, MSVCRT is now the only ignored default library
added dir "$(DXSDK_DIR)\Lib\x86" to linker -> general -> additional library directories
added dir "$(DXSDK_DIR)\Include" to c/c++ -> general -> additional include directoriesdirectories
make sure you have directx sdk installed and environment variable 'DXSDK_DIR' set correctly
removed functions calls leading to asm (.s) files (in sys_win.c):
Snd_WriteLinearBlastStereo16(), Snd_WriteLinearBlastStereo16_SwapStereo(), SND_PaintChannelFrom8(), SND_PaintChannelFrom16(), Sys_LowFPPrecision()
removed id386 define (so asm files are completely out of the game)

now there are ONLY libpng.lib warnings of this type: "locally defined symbol * imported[ in function *]"
gldebug comiles for me with 0 errors and 26 warnings
