Try this: open Registry Manager and search for "addressbook" - I think it should be there for all XP installations. It will find the entry, highlight it, select it, but Remove is not enabled.
I think it only happens for entries that do not have an uninstaller registered (AddressBook is one, Fontcore is another one, etc. - to find these I used an app called MyUninstaller).
Also, is the Uninstall button ever enabled? It seems to be disabled for me all the time ...
thank you