When using Visual Studio 2008, under Project properties tab Build you can set the 'Platform target' to x86, x64 or Any CPU.

I never paid eny attention to this, untill now, because my OS changed from x86 to x64. When I compile an application with platform target 'Any CPU', does this mean that my application runs both under x64 and x86, or should I compile 2 diferent versions, 1 for x64 OS and 1 for x86 OS?