Office does not like to be copied from one hard drive to another,
because that is one method a software pirate might use in order
to bypass the Office activation process. If you have your Office
CD and the 25-digit product key, then:
1. Download the Windows Installer Cleanup Utility from
http://support.microsoft.com/?kbid=290301 and install it.
2. Use the utility to delete the Windows Installer registry
entry for Office.
3. Reboot.
4. Uninstall Office by clicking on Start | Control Panel |
Add or Remove Programs | Microsoft Office | Remove.
5. Reinstall Office from the original CD.