A reinstall would give you more faith in your system. If you're using an upgrade disk, you just need to have the disk you upgraded from to do a clean full install. you'll first run the xp cd upgrade, formate the drive and at some point it will ask for your Windows98 or what ever CD. insert it and let it verify and then put the xp back in.
Be sure that you have your product key, if you don't, there is a program called jelly bean that will get it for you.
The easiest way to do all of this is to go buy a new hard drive and install the OS and then hook up the old drive as a slave. Don't ever hook up both drives and do a new install--while I'm at it, unplug all usb stuff on a new install.
I just bought a Seagate 120 for $39 dollars last month and did just what I'm suggesting to you. It got rid of all of the little bugs!
