ERROR_INSTALL_NOTUSED 1634 Component is not used on this machine

ERROR_INSTALL_NOTUSED 1634 Component is not used on this machine.
Suddenly I cannot run any of my office 2003 applications. I tried to run Word, Publisher, Excel or PowerPoint, I get the following error:
"MS [office application Name] cannot install the necessary files due to windows installer error 1634.
Component not used on this computer"
Since the last time I have used Office on this computer, I have not installed any programs, updated any programs or exposed the computer to any of the Black Tuesday stuff.
Any Ideas?
Thanks in advance.
