You will need to clean the registry. You can google registry cleaners. Make sure that you search for reviews before you decide to use one, and that you make a backup of your registry. One wrong move in the registry, and you could render your pc useless… A cleaner that a lot of folks here have used (myself included), is cccleaner.
The best method, would be to format your pc and do a fresh install of windows, then reload all of your stuff. Just make sure you make a backup of anything that you might need. Formatting wipes out everything on your hard drive.