What Microsoft's scripting team says about changing the registry (from the Tweakomatic page):

As you probably know, Microsoft has a sort of love-hate relationship with the registry. The registry is the configuration database for Windows and Windows applications, and many options can only be set by manually changing a value in the registry. For example, if you’ve ever read a Microsoft Knowledge Base article, you’ve likely seen a sentence similar to this:

“To correct this problem, change the following value in the registry.”

Now that’s fine, except that this sentence is invariably followed by a disclaimer similar to this one:

Warning Don’t ever change a value in the registry. Ever. We know we just told you to do that, but would you jump off a cliff if we told you to? Don’t ever change a value in the registry. Don’t even say the word registry. We know a guy once who said the word registry, and three days later he was hit by a bus. True story. As a matter of fact, you shouldn’t even have a registry on your computer. If you suspect that you do have a registry on your computer, please call us and a trained professional will be dispatched to your office to remove the registry immediately. If you accidentally touch the registry, wash your hands with soap and water and call a doctor. Do not swallow the registry or get it in your eyes!
Now, to be honest, some of those fears are a bit exaggerated, and the disclaimer is there largely for legal reasons (remember, this is the day and age when you can order hot coffee in a restaurant, and then sue the restaurant when the coffee they give you turns out to be, well, hot). If you do it correctly, changing the registry is perfectly harmless. At the same time, however, it’s true that there are certain values in the registry that should never be changed; in fact, changing them can pretty much wipe your computer out, once and for all. It’s like working on the bomb squad: if you snip the right wire, the bomb is defused and everything is fine. But if you snip the wrong one—Boom! You just created Microsoft Bob!

Um, not that we’re saying Microsoft Bob was a bomb or anything ….

With those cautions in mind, editing the registry can be safe if done with care. That's a good thing, because some things can only be accomplished by editing the registry. Just make sure you make a backup of your registry before making any changes!