Windows registry is a complex of control settings deep inside the heart of your Windows operating system. There are literally thousands of commands, classes, and keys that can all be modified. Unless you know exactly what you're doing, unless you know how to recover from any damage that you may cause, its best to leave the registry alone. Editing the registry can lead to a non-functional operating system. Luckily you can make the changes you need indirectly using the freeware Tweakui which lets you change 100s of settings.

If you're really interested in learning more about your registry, there are good books on the topic which I recommend. If you're just the casual Windows user, then this is not a topic that is worth your time.