Then it will be pointless in getting 4GB of ram since XP Pro only sees at the most if you are lucky like 3.8gb or something like that. Also 64 bit will still play 32 bit programs I believe I could be wrong but I am pretty sure they work. I used XP 64 bit before I went to Vista 64 and all my programs I have ever put on either work just fine.

But XP will see 3GB Im pretty sure.