Hmm...I have simulated your warning by setting the runtime switch to Multi-threaded Debug DLL (/MDd) as you have. Did you do a clean build after changing the switches (Build menu, then Rebuild...)?
I just forgot to remove limbct from the exclude list here is my new log
Build Log Build started: Project: game test, Configuration: Debug|Win32
Command Lines Creating temporary file "c:\Users\user\Documents\Visual Studio 2008\Projects\game test\game test\Debug\RSP00000151686064.rsp" with contents
[
/Od /D "_MBCS" /Gm /EHsc /RTC1 /MT /Fo"Debug\\" /Fd"Debug\vc90.pdb" /W3 /c /ZI /TP ".\source.cpp"
]
Creating command line "cl.exe @"c:\Users\user\Documents\Visual Studio 2008\Projects\game test\game test\Debug\RSP00000151686064.rsp" /nologo /errorReport:prompt"
Creating temporary file "c:\Users\user\Documents\Visual Studio 2008\Projects\game test\game test\Debug\RSP00000251686064.rsp" with contents
[
/OUT:"C:\Users\user\Documents\Visual Studio 2008\Projects\game test\Debug\game test.exe" /MANIFEST /MANIFESTFILE:"Debug\game test.exe.intermediate.manifest" /MANIFESTUAC:"level='asInvoker' uiAccess='false'" /DEBUG /PDB:"c:\Users\user\Documents\Visual Studio 2008\Projects\game test\Debug\game test.pdb" /DYNAMICBASE /NXCOMPAT /MACHINE:X86 kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib uuid.lib odbc32.lib odbccp32.lib
".\Debug\source.obj"
]
Creating command line "link.exe @"c:\Users\user\Documents\Visual Studio 2008\Projects\game test\game test\Debug\RSP00000251686064.rsp" /NOLOGO /ERRORREPORT:PROMPT"
Output Window Compiling...
source.cpp
Linking...
LINK : C:\Users\user\Documents\Visual Studio 2008\Projects\game test\Debug\game test.exe not found or not built by the last incremental link; performing full link
LINK : warning LNK4031: no subsystem specified; CONSOLE assumed
LIBCMT.lib(crt0.obj) : error LNK2019: unresolved external symbol _main referenced in function ___tmainCRTStartup
C:\Users\user\Documents\Visual Studio 2008\Projects\game test\Debug\game test.exe : fatal error LNK1120: 1 unresolved externals
Results Build log was saved at "file://c:\Users\user\Documents\Visual Studio 2008\Projects\game test\game test\Debug\BuildLog.htm"
game test - 2 error(s), 1 warning(s)
Basically, 'cleaning' will delete all previous compiled intermediary files and marks all source files for recompiling.
You could try the debug version of the compiler switch (/MTd) for your debug build.
It my also be worth creating a new project (with one of the DarkGDK wizards), just in-case something has accidentally been changed in the projects properties.