As part of its Clean Up scan, the Windows Live OneCare safety scanner offers a free registry cleaner. Running this scan is a great way to rid your PC of clutter and keep it running at its speediest.
What is the registry?

The Windows Registry is the place on your PC where Windows stores information it might need to retrieve later—for example, when you open an application or change a system setting. The registry contains profiles for each user, the applications installed on the computer and the types of documents they create, what hardware exists on the system, and the ports being used.
Why should I clean my registry?

Over time, the Windows Registry can begin to contain information that's no longer valid. Maybe you uninstalled an application without using the Add or Remove Programs function in the Control Panel, or perhaps an object or file in the registry got moved. Eventually this orphaned or misplaced information accumulates and begins to clog your registry, potentially slowing down your PC and causing error messages and system crashes. You might also notice that your PC's startup process is slower than it used to be. Cleaning your registry is the easiest way to help avoid these common problems.
How do I clean my registry?

The Windows Live OneCare clean up scanner will find and remove any invalid registry items on your PC. It's easy—it’s part of a full-service Windows Live OneCare safety scan. Or, for a targeted approach, click Clean Up Scan in the Clean Up Center. The clean up scan will check your registry and locate any it