[monkey2468]

Depends on what you want. If you just want to upgrade xp then run disk from within XP. If you want BOTH xp and vista, do the following.
Install the upgrade as a seperate install without inputting the serial code at that start. (choose to input the serial later) Boot into the new vista OS (dual boot) and then run the update disk again but from the new vista OS. (upgrade the upgrade!) Then activate vista. I bit of a loop hole in the upgrade vista version as you get a full vista install instead of just an upgrade.

---------- Post added at 19:12 ---------- Previous post was at 19:11 ----------

Originally Posted by DaiNasty

Probably worth trying the dual install, although I'm not certain if it actually checks for an installed XP.

http://www.vistarewired.com/2007/02/...a-upgrade-disc

If it looks for a valid XP installation I'd guess you're stuffed.

It doesn't check for xp, just that there is a microsoft OS present.