one way to avoid having to reinstall is to use the sysprep tool found on the windowsxp cd. after running sysprep you can do one of the following:
1. shut down, replace hardware. When you turn on the pc after the hardware upgrade, winxp will reinitialize and reinstall all the hardware.
2. restart the pc, with a bootable floppy that has norton ghost on it. ghost your drive as you normally would, then follow the above step.
the only diff with those two steps, is that you will have a ghost image of your system should something go wrong. If this fails, you can always do a full reinstall and then get your important files, save games, and other docs from the ghost image using ghost explorer.
Personally i have done this several times and never had an unstable system afterwards.
Good Luck