Registry Mechanic is a program that will allow you to clean your registry. It removes issues and can really speed up your computer. That said, note this disclaimer:
DO NOT MESS WITH YOUR REGISTRY IF YOU ARE A BEGINNING USER.
Yes, I just typed in all capitals. Very important point there.
You have to sign up here to get a free license key:
After doing so, you can download the tool from here:
(be patient, everyone on the Internet seems to be trying to download it)
The second Web site has an excellent explanation of what the tool does:
The Registry on a new PC is compact, efficient, containing only the entries required to run your installed applications. And that's great, but this happy state of affairs doesn't last long. As you add and remove other programs, so orphaned entries are left behind, with the result that the Registry just keeps getting larger. Over time it'll consume more RAM, and take a little longer to locate Registry values, slowing your PC down.
Recommended for more advanced CIS 101 students and students beyond, but make sure to set a System Restore point first. If you don't know what System Restore point is, it's probably not a good idea to download this.
Also - once you get the tool, run a deep scan on your registry, fix the problems, and then let it compact it. Even in the 45 days or so since I last ran the tool, I had 200+ errors in my registry!