Clean your Windows registry

By Don Reisinger

The Windows registry may be the least understood tool in Windows. At the same time, it is the most useful for those who like to tweak and fiddle with the operating system manually. For most people, though, just the sight of the registry is enough to make them stand back in horror, kind of like Macaulay Culkin in Home Alone.

For all of its ominous menus and its strange appearance, though, the registry is not as complicated as you might think.

Compare it to a Windows brain. When you are first born, your brain is relatively free of information and knowledge. As you are growing up, finding interests and learning, the brain becomes filled with critical information that helps you understand the world around you and perform daily tasks. So it is with the Windows registry.

So what's inside? When you install a program on your computer, Windows adds critical information about the program, as well as where it is stored and what files it opens or can change. Of course, that's not all. Windows keeps the following information in the registry:

• User information like the account name and account icon
• Property settings for each folder
• Hardware information such as the type of processor in the machine (for instance, Intel Pentium or AMD Athlon), as well as the mouse and keyboard brands, to name a few
• Ports 'or entry and exit points for data to pass through' that are in use
• System information including BIOS version and the installed Windows operating system
• Devices connected to the computer such as external hard drives or an iPod.
• The configuration of the computer in its present state. This can include such information as the colour scheme of the Windows interface and the chosen font displayed on all of the windows.
• Installed software with information containing versions, updates, as well as its respective location on the hard drive.

Now that you know what it does, let's go inside and have a careful poke around. If you like, try following along on your computer. To get started, let's open up the registry with a program called regedit. Click Start, then Run. Type regedit into the dialog box and click OK. The registry editor will open.

WHAT'S IN THE REGISTRY?

When you first enter the registry, you immediately see a panel on the left side with five headings in a "tree-view" format and a panel on the right side that will show the information in the given folder. Following along the lines of the previous example, think of the five sections on the left ' each beginning with HKEY (for "Handle to a Key") -- as five drawers in a filing cabinet, each with its own unique function and content.

HKEY_CLASSES_ROOT (HKCR) contains information about registered applications and file extension associations. In other words, HKCR tells you which file extensions, such as .doc or .xls, correspond to given programs on your computer (in this case, Microsoft Word and Microsoft Excel, respectively), as well as various pieces of information regarding the software on your computer. Applications lookup values in the HKCR section to find preference settings and version information before the program starts. Any changes made to a program are immediately saved in this directory.

HKEY_CURRENT_USER (HKCU) stores all of the information and preferences regarding the user who is currently logged on. Continuing our brain example, HKCU is like a biography. It reflects your preferences for how the operating system looks (for example, Windows classic view or the default Windows XP look), user settings such as desktop theme and screen savers, and all other information about your account. Any changes made to the user account get saved in this area of the registry. They might include something as simple as changing your desktop background, or as complex as manually changing Windows’ appearance.

The third heading is HKEY_LOCAL_MACHINE (HKLM). It contains settings that are common across the whole computer and shared by all of the users on the machine. It contains hardware, security, and system information to name a few. HKLM acts as the centerpiece of the entire registry. It is the location where most manual cleaning will be done.

Just below HKLM is HKEY_USERS (HKU). HKU keeps all of the individual information found in HKEY_CURRENT_USER under one tab. If HKCU is representative of your biography, then HKU is representative of each individual's biography in your family. All of the information that is kept in HKCU mirrors information about a given user in HKU.

Finally, let's look at HKEY_CURRENT_CONFIG (HKCC). HKCC contains all the information gathered when the computer is booted up. Unlike the previous headings, HKCC information is entirely new each time the machine is turned on and removed when the machine is shut down. Common information stored in HKCC includes fonts and Internet options. Typically, you touch this section only rarely when the time comes to clean the registry.

WHY CLEAN THE REGISTRY?

As time goes by, the registry becomes filled with increasing amounts of information, including a lot of junk. Unnecessary and obsolete information fragments clutter the registry and this can create a drastic loss in performance. This can slow system response, cause frequent crashes, and create a variety of software problems, such as recurrent shutdowns and slow program response.

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