Kathy,
There are many different views held here re your question.
IMO the best generic advice is -
If you do not have knowledge of the registry, then you would probably be better off leaving it alone, and definitely not placing blind trust in a program to do the job for you.
To advise anyone that a "Registry Cleaner" works, and that it will fix or speed up their machine {or all the other nonsense that is often propagated about these things} can mislead people.
Should you decide to go ahead -
Make sure you have
1.a current System Restore point created.
2.a recent "Back up" of your computer- preferably to an external HD.