Should I upgrade my 32-bit processor to 64-bit?

You won't notice any difference running in 64 bit mode because almost every program you have will have to still run in 32 bit mode, even if it says it is made to work with the 64 bit version. Now as far as moving up to a socket 939 system, yes, you will notice a big improvement because the way it sends data from the RAM to the processor. I actually run 32 bit XP on a dual core 3.2 Athlon because I have found XP 32 bit the fastest with my programs, and the best compatibility.