There is no magic bullet when it comes to "cleaning" your registry. I've been in the desktop computer repair business for longer than I care to admit (or can remember). I get at least 5 to 8 calls a month from some poor individual that bought a registry cleaner and when they installed and ran it all heck broke loose. At best it screwed up some settings and at worst it left them with a computer that won't boot.

The short definition of your registry is that it contains information about hardware, software, and user settings. Every time you add, remove, or change a piece of software, or hardware, or a user setting it is recorded in the registry. The registry is setup as a database that holds all these settings for access when needed.

There are as many settings as you need for all the software, hardware, and users installed. This is a huge amount of information and it continues to grow as you use your computer. In fact this database is so big it is stored in five different files and locations based on the type if information. These files are often called the "hive".

So every time you install something new or make a change to a user setting you are adding information, sometimes in multiple places, to this registry database. Over a period of time with lots of installs, a few uninstalls that don't remove all of the settings, and changes to the operating system, you end up with a bloated registry.

When you desktop computer boots up, it runs through this database to check for settings. As you use your computer everyday, each software or hardware device may access those settings too. The bigger the registry, the slower it gets to access and boot. Throw in a few hundred thousand extra settings and it can really get sluggish going through settings that don't even matter.

So enter the registry cleaners. The registry cleaners go in a look at each setting and try to determine if it's a valid setting (relates to installed software, hardware, or user setting) and if it can't find a reason for it to exist, usually erases it. Can you see the tremendous opportunity for a screw up here? It's inconceivable that any single company can track all the possible changes (sometimes in multiple areas).

The registry is not designed to be altered by hand except for knowledgeable technicians due to the complexity and thousands of settings that are pretty much unlimited. Software and hardware vendors create 100s of changes when they create an install routine for their product. I don't care how good the registry cleaner developers are; they can't possible keep track of those types of changes with so many variables.

If the registry cleaner is aggressive in their changes, chance are very good that you will suffer some necessary entries being removed. Depending on what settings are changed, you may not have access to some software or hardware, and of course the worst case is if the setting is necessary for your desktop computer to boot.

The best policy is to back up your registry before you make any changes. You can find out how by just going to the Windows Help on your version and it will give you a step-by-step method. But restoring a registry is no simple task if your computer won't boot and may overwhelm most everyday users. Like I mentioned earlier, there are five separate files that all go to very specific locations. If you have your Windows Install CD, you can go into the Recovery Console and that does make it easier but it's still not a lot of fun typing in all those directory paths.

The bottom line is if you do try out a registry cleaner, always make a backup of your registry first and have some kind of restore plan. Then if the worst case scenario does occur (unbootable desktop computer), you will still be able to recover with a minimum of time and trouble.