I put my Web Spider code onto my x64 system. Everything is managed code. I was able to just start running the code. The lesson seems to be that if you right 100% managed code, your code will run, your code has a pretty good change of running in 32 bits or 64 bits. I always hate to say something will run a 100% of the time, but my guess is that it has a good chance of running. Perhaps someone from MS can post a comment about the pitfalls of 32 vs. 64 bits in .NET 2.0.