WHAT IS THE REGISTRY

by Lee Alexander

In Windows operating systems, the Registry is a special file that holds structured data about the system's hardware, user preferences, and other configuration data. The purpose of the registry is to reduce the number of earlier configuration files: AUTOEXEC.BAT, CONFIG.SYS, WIN.INI, and SYSTEM.INI. Viewable as plain text, it was easy to modify these files and cripple the operating system. In Windows XP these files are eliminated.

There's a good reason why Microsoft made it inconvenient to play in the Registry. My first piece of advice is “ leave it be .” Unless there is a real Registry problem, or your curiosity surpasses that of a cat, it is best to let the Windows operating system do its own house-cleaning and maintenance of this entity.

How to Get There

You will not find a registry editor under system tools, like Disk Cleanup and Disk Defragmenter. Exploring the Registry can be a highly dangerous pursuit. It is a tightly constructed database and an inadvertent entry could cause your system to not even boot up.

If you do a search for Backup in Help and Support, you will find rather confusing text with a lot of cautions. Any mention of the Registry in literature or popular magazines begins with an admonishment to backup the Registry before proceeding any further. Registry entries must be very specific in format; a misplaced character can render your system inoperable.

An excellent utility for backing up the registry is ERUNT (Emergency Recovery Utility for NT systems) by Lars Hederer. You can find it at www.larshederer.homepage.t-online.de/erunt. Be sure to read the text file before you use the program. A companion utility, NTREGOPT, can be included in the download. That name stands for NT Registry Optimizer, a compactor utility.

What REGEDIT shows-

The structure of the registry is broken up into what are called hives. The five principal hives are:

Below is a screenshot of the expansion of one of the hives

Below are the data for a backup program (not a Registry Backup program) I downloaded. The key, SN (serial number), was added when I paid for an expanded version of the free program.

This screenshot shows the Registry entries for another free utility.

Note the complex data field for the application identity key. Corruption of a single digit, accidentally or intentionally, would disable the program.

Let's look at the functionality on the hives:

• HKEY_CLASSES_ROOT - associates filename extensions with applications.

• HKEY_CURRENT_USER - contains information for the presently logged in account

• HKEY_LOCAL_MACHINE - defines the state of the system. It includes data on bus types, system memory (RAM), installed hardware and software, and security settings.

• HKEY_USERS - entries are global, that is, they apply to all users.

• HKEY_CURRENT_CONFIG - the data refers to hardware not specific to any account.

• HKEY_DYN_DATA – DYN refers to dynamic or changing; contains data about presently installed PnP (Plug and Play) devices.

Examples of Registry Editing

You must be very careful to be in the correct hive when making changes or adding new entries. Using the Find function in the Edit menu may not take you to the correct hive. The bar at the bottom of the Registry window will give you the full path to the registry key selected. Before you edit a key or create a new one, be sure to make a written note of the exact spelling and value you apply.

The first example is rather trivial and intentionally so. It simply moves your wallpaper (if you use such) to give a clear area for desktop icons. For most systems the keys will not exist in their version of the Registry, giving us the opportunity to create a key from scratch. The key values will set the origin in the X. and Y dimensions for the position of the wallpaper. The values are in units of pixels, measured from the upper left corner of the screen. Since it's your Desktop, we want to be in the hive of the current user. Starting in HKEY_CURRENTUSER | Control Panel | desktop, create a new key by right clicking in the right hand pane, expanding New and selecting String Value. Enter WallpaperOriginX as its name. Double-click this new key and enter a value, say 100, for the pixel displacement from the left edge of the screen. Repeat the above for a key entitled WallpaperOriginY and use a value of 50 pixels for the vertical displacement.

Minimize the Registry to the Taskbar. There is no need to do a Save operation and that's part of the danger, your changes take immediate effect. On your Desktop, right-click and select Properties to refresh the display when you click OK. If the display is not to your liking, return to the Registry, right-click the appropriate key, select Modify and enter a new value.

The next example reduces the default times to close applications. Windows is rather patient when it comes to “hung” programs, the interval before the End Program dialog box appears. Again we will confine our changes to the current user by starting in HKEY_CURRENTUSER | Control Panel | desktop.

We could do away with the End Program dialog box entirely; however, this could stop a process (as opposed to application) prematurely with undesirable results. The key to stay away from is AutoEndTasks; leave it with the value of zero. A key we can modify is the HungAppTimeout, whose default value is 5000 milliseconds or 5 seconds. You can safely reduce this to one second or less but avoid zero. The second key in this category is WaitToKillAppTimeout; default value 20,000 ms or 20 seconds. You can safely reduce this timing to a reasonable few minutes.

Another recommended Registry tweak is a key to remove from memory DLLs (Dynamic Link Library) used by an application when the application is closed. Most versions of the Registry will have the key; if not you can create as described above. The key is AlwaysUnloadDLL and its default value should be set to 1 (for true). The location is HKEY_LOCAL_MACHINE | Software | Microsoft | Windows | CurrentVersion | Explorer.

Registry Cleaners

At the March 14, 2006 meeting of the Macon Users Group, the presentation was cleaning and optimizing your systems software. One of the topics was Registry cleaners. An article on the subject can be found on the Muggings page of the club's web site, www.maconusersgroup.org .

The following information is available in the article and I repeat the sources as a convenience. http://articles.networktechs.com/138-p1.php - a review of 5 free programs.

For compacting Registry, try RegCompact.net v1.8 from http://experimentalscene.com/download.php .

CCleaner.exe from www.ccleaner.com - multipurpose cleaner.

RegShot; find it at http://regshot.yeah.net/ - takes a before/after snapshots and records a log of changes.

Conclusion

In good conscience, I must repeat my warning to enter the registry with extreme caution. That is not to say it should be a grand unknown of the operating system, we have plenty of those in Windows OS's. This article has attempted to take some of the mystery out of a very complex and sensitive database. Random excursions can have high consequences, to the point where the only solution is a complete reinstallation of Windows.

In addition to cosmetic appearance and the management of applications, the Registry also holds many parameters for Services. Deletion or corruption of a Service could also render your system inoperable. The examples provided were gleaned from computer magazine articles written by experts. They were in no way found by yours truly "just playing around." We may do that in an application, where we could uninstall and reinstall the program; but never in the Registry.