How do I upgrade a Dimension 3000 with XP Home SP2 to XP Pro using a 2 year old retail XP Pro CD? When I attempt to upgrade with the CD, the operation halts and tells me that it can't continue because the OS on the computer is newer than one on the CD. I can't afford to wipe my computer clean and do a clean install and I really don't want to spend more money for yet another OS (retail XP Pro SP2) after already having paid for two prior OS's.

As a side note, does anyone know how to remove the junk the upgrade attempt left on my computer? After the failed attempt, whenever the cmputer reboots, a menu option appears asking me if I want to either continue with the install (which will fail) or if I want to boot to the OS. I can get rid of the psetering menu by editing the boot.ini file, but I want to get rid of the underlying files.