Office Source Engine error: Error 25090. Office Setup encountered a problem with the Office Source Engine, system error: -2147024703.
The Office Source engine (Ose.exe), which gets copied to your hard drive during Office installation, and which copies additional Office 2003 installation files from the CD to your computer when you modify your setup, has somehow become damaged or corrupted. Without a properly functioning Office Source Engine, you can't change anything about your Office setup.
If you're lucky, you'll be able to solve the problem by recopying Ose.exe from your Office CD. Insert the CD into your CD/DVD-ROM drive and use My Computer to navigate to the Files\Setup folder on the CD. Right-click Ose.exe and click Copy. Next, navigate to the PROGRAMFILES\COMMON FILES\MICROSOFT SHARED\Source Engine folder, click Paste, and then Yes to replace the existing file. Cross your fingers and re-attempt your setup. If recopying the Ose.exe doesn't work, you'll have to uninstall Office, through the Windows Control Panel, and then reinstall it. (If you upgraded, you'll need to have handy the CDs from your previous version.)