without using regedit, have you just tried to run the installer for it off of the install discs? If you don't have one, I'd download a copy of it from microsoft.
http://www.w7forums.com/official-win...ds-t12325.html
http://answers.microsoft.com/en-us/w...f-3ca30356fc3d
This isn't pirated copies either, it's ones Microsoft put out. I forget where it is in the options tree but if you look around while running it (not from disc since you aren't reinstalling, but mount iso to run or make a cd/dvd) you should see the option to install it back. It should fix the registry errors by overwriting it as it makes new entries.