OEM Office 2000 won't work

[Buck]

I upgraded from Me & my OEM version of Office 2000
refuses to work (it was OK using Me). I can't uninstall
it or reinstall it. I get the following message when I
try to reinstall:

"This patch package could not be opened. Verify that the
patch exists and that you can access it, or contact the
application vendor to verify that this is a valid Windows
Installer patch package."

I've tried the Windows install cleaner to delete the
previous registry settings but that didn't work either. I
had the same problem with MS Project but I was able to
reinstall it (it's a store purchase version).

Any ideas??
Thanks