Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Use the fixit mentioned in the following article to completely remove Office 2003 from the system and then reinstall it.
http://support.microsoft.com/kb/2639197
Note:
1> In case if you are unable to use the Fixit or if it does not help, try the method 4 in the same article to manually uninstall Office 2003.
2> If you are using Windows 64 bit operating system, save the ‘Fix it’ on desktop before running it.