Sure it's not a Windows XP
service pack that is in Add / Remove Programs?
There's no such possibility on my PC! One has visions of XP disappearing up its own orifice
Best to backup all the userdata first, to an external drive or second disk.
Best practice in my opinion is to have 2 partitions or even better 2 physical disks, so that you can install Windows on C and store all data on D.
That way you can more easily recover from a re-install. Of course, the default path for all Userdata is to the Documents and Settings folder on C, so you either have to remember to copy that (or back up) regularly to another drive, or else set the path to the D drive.
SD