QuoteIt is crucial that you say 'processorArchitecture="*"' in the manifest file. If you mention ''processorArchitecture="x86"', your application will not be able to launch in 64 bit Windows.
blog from Junfeng Zhang (http://blogs.msdn.com/junfeng/archive/2004/11/02/251318.aspx)
Strangely, the "assemblyIdentity" type must remain as ="win32". If you specify "win64" or "*" it doesn't work.
I also found it strange that the 64bit libs are still all something32.lib, e.g. user32.lib.
P.S. Microsoft seems to use processorArchitecture="amd64" in their own manifest files, I had to open up one of their progs to find this out beause the only official documentation I could find was refeering to Itanium 64bit apps. See this thread (http://board.win32asmcommunity.net/index.php?topic=22088.0).