|Just a guess here:|
Back up all critical data.
Unplug the printer from the computer - go to the printer settings and remove the printer icon - check the Device Manager and remove any printer devices. - In Windows Explorer, remove the printer folder - see if you can install a registry editor such as RegCleaner to name one of many. In RegCleaners default view you will see a list of programs installed to the registry, check and remove your printer references. Then run the cleaner to remove all old entries. Being an 'upgrade' from XP to Vista, there will be many. When you reinstall the printer, don't plug the printer into the computer until prompted to do so by the Vista driver install software.
Try installing the registry cleaner before doing anything. I don't know if you'll find one compatable with Vista.
All that being said; this is one of the many reasons why a 'clean' install is a better option than upgrading.