Possible Duplicate:
What does the Visual Studio “Any CPU” target mean?
We have a WPF application that must work on plenty of Windows machines from Windows XP x32 to Windows 8 x64. Our app includes NHibernate and SQLite. We do not need any feature of x64. How can modify application to run without any problem on all architectures?
Unless you have both the 64bit and 32 bit dll's of your external dependences I would just compile for the lowest common denominator i.e: x86 it will install and run correctly on both 32 bit and 64 bit versions of windows.
Compile it for the AnyCpu architecture, this will make it x86/x64 agnostic.
Of course this won't prevent issues if you are looking to access bitness specific things like %PROGRAMFILES%, if you do this you will still need to test for bitness using the Environment.Is64BitOperatingSystem property.
