did you back up your registry before you messed around with it?
did the program output a logfile of its actions anywhere?
I can't say I'm the expert at these things, but if you can restore your registry from the backup that's the way to go.
otherwise it might be helpful to other forum members if there was a log file to post it here in [ code ] tags
and i'm sure you know this now, but messing around in the registry doesn't have to be dangerous, but it certainly can be. I'd be wary of any registry optimization program that doesn't warn you ahead of time that you're fully capable of messing something up.
also it's helpful if you go into some more detail about your dvd drive. what brand/model is it? you said it doesn't work...what doesn't work? no power/lights? doesn't open? discs don't spin? spins but doesn't read discs?