Moving to AMD from Intel means a new Motherboard. Your existing HD has all it's critical files set to work with your current Intel motherboard and won't jive with the AMD board.
Its annoying, but backup all the data you want to keep ontoa DVD or whatever, replace your parts and begin to wipe your HD clean to reinstall XP to the new board.
Workarounds arent the best solution, take the time to do it properly and you'll minimise the risk of problems later down the line.