Well, I originally bought XP Pro for another machine I had. It was a Duron 900, 384 MB RAM, and 20 GB hard drive. Then I built a new comp with Athlon XP 2400+, 512 MB RAM, 80 GB drive, totally new from the ground up. Installed XP on there like 2 times. Then with the same system, I added 2x74 GB Raptors in RAID 0, and since have installed XP Pro twice on that setup. Installation total of 5 times. I dunno. Hopefully I will never have to call MS. We sometimes have to call at work to activate XP on the computers, and its a real pain, waiting on the phone forever.