Before you mess around with the registry, it's best to to create a backup copy of the registry and to also save any important data to an external hard drive or disk. Some registry-cleaning programs have a feature to back up a copy of your system's registry. If not, a simple Internet search should lead you to a free backup program.
Windows has a built-in program for editing the registry. It's creatively titled regedit.exe and can be accessed by going to the Start menu, clicking Run and typing in the program name. While this program is easy to access, it's difficult to use. Registry entries have long, oblique names that don't say much about what they represent. Even savvy computer users may have no idea what a particular entry points to. So unless you have specific instructions for how to alter or delete a clearly defined entry, it's best not to experiment with regedit.exe.
Third-party registry-cleaner programs are plentiful and remove a lot of the confusing grunt work of parsing and deleting registry entries. To find a program that suits you, check reviews on sites like ZDNet, CNET, PC World or PC Magazine. Some of these programs are free or only fix a few entries at a time, which can be quite laborious when a registry may have 2,000 broken entries. Others may cost $20 or more and may come as part of a package of system utilities.
It's not necessary to clean a registry more than once a month. Using a disk defrag program may provide additional performance boosts.
Before you run the program you've chosen, make sure you close all other open programs, as well as those running in the system tray, next to the clock in the bottom right corner of your screen. Follow directions closely: Most of these cleaner programs are intuitive, first scanning the registry for errors and then offering choices to fix broken entries, but you may miss an important step or warning if you click madly and try to speed through the process.
Some experts recommend against using programs that automatically delete registry errors [source: Bass]. Instead, it's better to approve deletions manually. The cleaner will likely offer a list of registry entries that it's safe to delete because they are certainly obsolete. It may also provide an option to "repair" an entry. Going deeper and deleting borderline entries could affect a program's ability to function, such as by deleting a DLL that the cleaner doesn't realize is shared by more than one program -- or you may irreparably damage your installation of Windows. When in doubt, let the entry stay.
And that's about it. Hopefully you managed to clean up a few hundred entries without bricking your computer. If not, well, then you probably can't read this anymore and won't be interested in the links on the next page about registry cleaners and other related topics.