I'm looking for a couple of Windows XP Home/Pro licenses for some additional computers I just built. Companion CDs are helpful too.

These computers aren't integral or anything, so I don't want to go blow $200 on retail copies, and would prefer to spend as little as possible. If anybody upgraded to Vista, or got sick of Microsoft and migrated to Linux and happens to have a LEGAL copy going unused, please let me know what you'd like to get out of it. Thanks.