Ok, so you felt like a true pro, and decided to go monkeying around with your registry... and it turns out you weren't a real pro, and your system is really messed up now.
This situation happened to me, and a visitor to the site (Miguel Romao) fixed me right up. Since he is not a member, and I thought his solution was so quick, simple, and easy, I decided to put it in a FAQ for future reference.
A - Start a pure dos session.. press f8 before windows start and select "Command Prompt" at the little menu. B - Type Scanreg /restore C - Select a registry backup from 2 or 3 days ago D - Restart
Done and done. Just be start up your machine in Safe Mode (if possible) and backup whatever work you have done before you do this, as it is most likely it will be lost after this procedure. But that is better than reloading Windows, which is what I was prepared to do before this solution was posed to me.
Obviously, the moral of the story is "Thou shalt not mess around with your registry unless thou doth knowest what thou art doing"