error C1854: cannot overwrite information formed during creation of the precompiled header in object file

I think you can find the answer here: http://social.msdn.microsoft.com/forums/en-US/vclanguage/thread/b3aa10fa-141b-4a03-934c-7e463f92b2a5/

Basically, you need to set the stdafx.cpp file to "Create Precompiled Headers" and all the other .cpp files to "Use Precompiled Headers"