Hi Oldgoat, and welcome to the forum.
There are one or two mature members on this forum, the writer included, and I'm sure you could learn a lot on here either by simply observing, or better still, joining in.
You don't have to actually know anything to do that. The lounge is for anything and everything, and not necessarily to do with computers, and you can also ask questions and pick brains till your hearts content.
Get any sort of problem with your PC, and you could probably find the solution here by posting your problem.
To your question. Until you pick up some knowledge about PC's in general, and the registry in particular, I'd suggest you leave it alone for now. You could do a scan for issues if you need to satisfy your curiosity, and see what sort of list you get, but don't fix them.
Have a good read of the CCleaner Guide, a link to which you'll find in my signature at the bottom of this window, and if you don't already know, learn how to do a "System Restore", and how to make sure it's actually on and monitoring your C: drive.
System Restore:
This is assuming you have XP.
Post back here, and give us some basic info such as which operating system you run (XP, Vista), and we can then give you some basic guidance/advice.
CCleaner is an exellent program for helping to maintain your PC, but PC's are complicated beasts, and can easily take a wobbler for seemingly no reason at all. It's therefore pretty important to know the basic methods of rescuing yourself from problems before you embark on something which could cause even a minor one.
Hope this helps, and look forward to seeing you on the forum.