Office 2003 Update problems

Hi!

I have an interesting problem, my Office programs (Office2003) all keep
having installation problems. Whenever I try to use update, add/remove
or use 'Detect and Repair' I get an error message from Windows
Installer....

" The installation source for this product is not available. Verify
that the source exists and that you can access it."

I have tried all sorts to fix this problem, updating windows installer,
reinstalling all the Office apps (this can only be done after using the
Windows Install Cleanup Utility!!) but the problem remains. I suspect
kb921566 of playing a part in this but of course it wont uninstall!
Listool is useless it just generates another crazy error and can't run.

Anybody any ideas? Please?

Thanks in anticipation!

Anthony