Try putting the master CD you got for Excel or Office and run the repair option, it worked for me after I uninstalled an application that took out a little too much and also removed ddl's needed by Access
the problem is I dont have the original cd rom and also I have since found that when my computer crashed it wiped out some files for microsoft office 2000 so although it is all still buried somewhere when I try and open Word or Excel it keeps telling me to install the installation 2000 disc which I dont have!!