I'd do a clean install rather than an upgrade. You can use Vista's "Easy Transfer" software to back-up your files and (some) settings by running your Vista DVD from within XP. You can also try the upgrade (first backing up your XP installation with a disk imaging program like Ghost or TrueImage) and test it to see if it works properly. If it doesn't then you can restore your XP image and try it the other way. When I attempted to upgrade from RC1 to RC2 it was a debacle. However a clean install revealed that RC2 was actually pretty stable.