This may be worth a try:
Go to Start, Run. Click Browse. Navigate to the folder that contains Powerpnt.exe. It may be at:
C:\Program Files\Microsoft Office\Office
Select the Powerpnt.exe file, and click Open.
In the Run dialog box, click your mouse at the end of the command line; type a space, and then type /regserver
The command should look like:
"C:\Program Files\Microsoft Office\Office\Powerpnt.exe" /regserver
Click OK.