Sounds like someone has been a very bad boy (or girl as the case may be) and
has installed an illegal copy of XP. So, you won't be able to do an upgrade
as that would be stupid of Microsoft to allow illegal copies of their
operating system to be upgraded. You are free to purchase any version of XP
you want and install it. Unless you are in a corporate or small business
environment you will be happy with XP Home Edition and save some money as
well.

"MSS" wrote in message
news
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.