Differences between 32 and 64-bit .NET (4) applications

Question

What are the differences between 32 and 64-bit .NET (4) applications?

Often 32-bit applications have problems running on 64-bit machines and conversely. I know I ca

Answer 1

In addition to other answers, I would like to add one more thing: we can run software of 32-bit system on 64 but conversely is not possible!