Kbase Article of the Week: Mac OS X 10.2: Remove Microsoft Office v.X Test Drive before installing Microsoft Office »

An oldie but a goodie:

Remove Microsoft Office v.X Test Drive if you cannot install Microsoft Office v.X.

If the Remove Test Drive application does not work, or if Office v.X is not recognized as the non-Test Drive version following installation, try deleting the Office v.X folder, then reinstalling the software.

If you need additional assistance, contact Microsoft Product Support Services (866) 474-4882.

FYI, that phone number still works.