Remove and reenter the Microsoft Office 2008 for the Mac product key

If your copy of Office 2008 was installed with an invalid product key, i.e., a sequence of 25 letters and numbers, you must reenter the product key to activate Office. The product key sticker is located on the back of the installation CD sleeve or case., or if you mistakenly used the same product key to install Office 2008 on more than one computer, you must remove the invalid product key and enter a valid product key to use Office 2008.

1) In the Finder, select /Applications/Microsoft Office 2008/Office/OfficePID.plist, and then on the File menu, click Move to Trash.

2) Select /Users/username/Library/Preferences/Microsoft/Office 2008/Microsoft Office 2008 settings.plist, and then on the File menu, click Move to Trash.

3) On the Apple menu, click Restart.

4) After your computer restarts, open any Office 2008 application.
The Office Setup Assistant opens.

5) Accept the software license agreement, and then enter your valid product key.
The product key is located on the back of the Office 2008 for Mac DVD sleeve or on the back of the Install Guide.