Well, I've felt your pain. Unless you have a registry editor (like PHM, or others) which will allow you to create a back up-or better yet a back up of your system, I don't see how it's possible to return the state back.
I too had the same small font issue, and was able to restore my registry with the PHM registry editor, and also a clip board (copy/paste) type prog that allowed me to copy the complete path to the back up reg file. It was VERY frustrating, and I had success only once.
Not that it's much help now, however, you should always back up your system before trying anything that will alter the registry.
Good Luck!