The main reason I have seen those is basically because a hard drive cleanup wizard was performed and the Office Installation Files were deleted.

So now everytime Office uses a new feature or attempts to update, it's giving you that error.

To backup a little here ,the Office Installation Files take away the need to have the Office 2002/2003 CD in the drive when you are installing, updating, or using a new feature. Actually sorta cool. But people will either intentionally or accidently remove this feature many times.

The solution to your problem?
There really isn't one to my knowledge. Maybe the Microsoft website's knowledge base can help, but I think they'll recap what I said above and say good luck (in a professional legalese sorta way). Good luck