How to Clean Your Computer's Registry

The Windows Registry is an enormous batch of files containing information about almost everything that occurs on the computer, from a visit to a Web site to a program installation. The registry also contains information about drivers and other essential programs, like DLLs -- small helper programs that often work with more than one application. This information is stored in the form of "keys" that help programs run. It's like a big blueprint for where everything goes on your computer and how it all fits together. Only computers running Windows operating systems have registries, and despite rumors to the contrary, Windows 7 will have a registry.

A registry may have hundreds of thousands of entries, and new entries are created all the time. As it fills with information, the registry may cause a computer's performance to suffer. One problem is that Windows almost never removes registry entries, even if a program is uninstalled, as most uninstallers aren't able to effectively remove their own registry keys. And as files are moved around and programs are uninstalled, some registry keys point to programs or files that no longer exist or are located elsewhere.

Fortunately, these errors don't have to be tolerated. The registry can be cleaned up, though not completely. And for your troubles, you may get better performance and decreased boot time. Some satisfied users report fewer instances of lag or Windows hanging (when the computer isn't responding). The exact performance boost varies depending on the state of the registry and the effectiveness of the cleaner program employed. You may also free up disk space, although most registry entries are very small.

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Registry cleaning is not without risks. This is a very sensitive area of your computer, and if you're happy with how your computer is running, don't go digging around. Trying to manually edit your registry can create errors in the registry that make it impossible to load Windows. Some registry-cleaning programs have been known to delete important registry keys or essential DLL files. And the performance improvements may be negligible, while running the program and approving each recommended deletion could take hours. In addition, reliable data on how registry cleaners affect performance are almost impossible to find. Most "performance tests" are actually produced by the developers of registry-cleaning tools.

Despite these concerns, it is­ possible to clean out some of the registry's gunk, and your computer may be better off for it. On the next page, we'll take a look at how to go about this delicate job.

Cleaning the Registry

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.