I have Microsoft plus! and did a reinstall after formatting with no problem. Look in Add/Remove Programs and see if it is listed. If so try to uninstall it and try again. Also look in Program Files in Windows Explorer and see if a file has been added. You can then manually delete it and try again. A quick go around with CCleaner and RegScrubXP might also delete any left over files from a failed install before you attempt a new installation. I don't see why you would have to buy a new copy.