Okay, I'm stupid. I put my new HD in, and left my old HD in as a slave. But when I installed XP Pro it felt it needed to leave my old HD as C and put my new HD as F, even though F was IDE 0 and is where windows was installed.
Anyhow, I tried to use the Disk Manager and it said I can't change the drive letter for my main drive, even though its the ONLY HD in my box now.
Am I gonna have to reformat again?