64-bit Windows contains both 64-bit and 32-bit versions of all the userland libraries -- things like user32.dll and comctl32.dll -- as well as both the 64-bit a

64-bit Windows contains both 64-bit and 32-bit versions of all the userland libraries -- things like user32.dll and comctl32.dll -- as well as both the 64-bit and 32-bit versions of .NET.