Trouble Installing Office 2003 after 2000 Beta Version

I recently found out that I had an illegal "beta" release version of Office
2000 on my machine. Since then, I have purchased a full Office 2003 Pro
(with the cute holographic disks and all), but it won't install. When I
try, it tells me that the key is invalid. I typed that thing in ten times
before I remembered reading in Google that the Office 2k service pack and
newer versions of Office are designed to react badly with the old
illegitimate versions. Is this the reason why the new one won't install? I
uninstalled the old version completely before trying the 2003 install. I
can reinstall 2000 and keep going with the old software until I figure this
out, but I'd rather legitimize the system.

I don't want to have to do a complete OS rebuild of my system if I can avoid
it. Is there a hidden file or a registry setting I can tweak to allow
installation of 2003?

- Magnusfarce