If you're not 100% sure that you know what you're doing, I wouldn't suggest manually removing registry keys. You may f*ck up Windows to the point where you would have to do a clean install. I suggest downloading a registry cleaner. CCleaner is free and does an okay job.
I agree with J0hn00, don't delete any keys until you know what they do, even after you know what they do, don't delete things unnecessarily from the registry. Ccleaner is a good tool; just be sure that you use the option of making backups.