>I'm seeing quite a few XP Pro for sale on eBay, but many say they are OEM. I know what that means, but how can I know that I'm getting the box version, not an OEM? Is there also a way to know whether the version on my PC is OEM or not? I positive it is not, but I want to be dead certain before I shell out $130 for it because from what I've read, you can change the key to the existing OS, but only if they match the current version of OEM/Non-OEM.

Also, can I install XP Pro, or change the key, using an upgrade version instead of the full retail version?

Update: Just called TigerDirect and they have the full retail version for $125. Guess I'll be making a trip at lunchtime...