Hi, I created a console project and it was compiled sucessfully with VS2008 RTM. After VS2008 SP1 was installed, the compilation failed with the following error: -------------------------------------------------------------------------------------------------------------------- Build Log [noparse] Build started: Project: Demo1601-02.vcproj, Configuration: Debug|Win32 Command Lines Creating temporary file "e:\VC_Pro\Projects\Demo1601-02.vcproj\Debug\RSP00000115723832.rsp" with contents [ /Od /D "WIN32" /D "_DEBUG" /D "_UNICODE" /D "UNICODE" /FD /EHa /MDd /Yu"stdafx.h" /Fp"Debug\Demo1601-02.vcproj.pch" /Fo"Debug\\" /Fd"Debug\vc90.pdb" /W3 /c /Zi /clr:pure /TP /FU "c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.dll" /FU "c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Data.dll" /FU "c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Drawing.dll" /FU "c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Windows.Forms.dll" /FU "c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.XML.dll" ".\Demo1601-02.vcproj.cpp" ".\AssemblyInfo.cpp" ] [/noparse] Creating command line "cl.exe @"e:\VC_Pro\Projects\Demo1601-02.vcproj\Debug\RSP00000115723832.rsp" /nologo /errorReport:prompt" Output Window Compiling... Demo1601-02.vcproj.cpp .\Demo1601-02.vcproj.cpp : fatal error C1853: 'Debug\Demo1601-02.vcproj.pch' precompiled header file is from a previous version of the compiler, or the precompiled header is C++ and you are using it from C (or vice versa) AssemblyInfo.cpp .\AssemblyInfo.cpp : fatal error C1853: 'Debug\Demo1601-02.vcproj.pch' precompiled header file is from a previous version of the compiler, or the precompiled header is C++ and you are using it from C (or vice versa) Generating Code... Results Build log was saved at "file://e:\VC_Pro\Projects\Demo1601-02.vcproj\Debug\BuildLog.htm" Demo1601-02.vcproj - 2 error(s), 0 warning(s) ---------------------------------------------------------------------------------------------------------------------- This is a project for only practicing purpose, not that critical. But I like to figure out the reason in case of that I may have the same problem in carrying out a real project in the future. Thank you.