Did you use a hard disk utility to clone the contents of the old drive
to the new drive? Office does not like to be copied from one hard drive
to another, because that is one method a software pirate might try in
order to bypass the Office activation process. To fix the problem:
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 entry for Office 2003.
3. Reboot.
4. Uninstall Office 2003.
5. Install Office 2003 from the original CD.