Try the fix at Kelly's Korner
.Lift Restrictions - TM, Regedit and CMD
- #275 on the left.
Right click on it and save the .vbs file to your desktop. Then, double click on the file icon (on your desktop) to run the script. You may need to reboot your computer for the changes to take affect.
With any fix like this you should create a new restore point and backup the registry
first. For backing up the registry I like to use ERUNT
This problem is most often caused by malware.