I have XP Pro Version 5.1 running but I do not have the original XP disk. I
tried to install the various upgrades via download as well as with a service
pack 2 disc. I get an error message that I have an unregistered copy of XP &
therefore can't do the upgrades. Can I purchase & install XP PRO as an
upgrade or do I have to buy the full program? Also, what if I want to but
a lower version of Windows rather than XP Pro.