By Kim Komando
Gannett News Service

Ever install a program or device that makes your stable computer turn into the creature from the digital dark lagoon? Fortunately, tools exist that allow you to send Windows back in time.

Both Windows XP and Windows ME include System Restore. It warehouses information about Windows and certain application files. When you need to restore the system, you pick a past day. System Restore takes Windows back to that time, undoing changes that might be causing your PC to misbehave.

System Restore creates restore points several ways. They are created automatically every 24 hours, assuming the computer is turned on. Restore points also are created when you install a program and sometimes when you add a device, such as a printer. Or you can create your own restore points.

To use System Restore, click Start, All Programs or Programs, Accessories, System Tools and System Restore. This will open a wizard. You will have a choice of creating a restore point or picking a restore date. To do the former, select that option and click Next. Follow the wizard.

To pick a restore date, select that option and click Next. A calendar will appear. The bold-faced dates have restore points.

If a program installation is responsible for your problem, select the installation date. The installation will be listed in the right-hand box. Select it and click Next. On the confirmation window, click Next. Windows will restore the system and reboot.

A restore point also is created when you run System Restore, so you can try another date if you don't like the result. If the restoration effort fails, it is automatically reversed. Pick another date and try again.

System Restore has a few disadvantages.

For starters, it's a space hog. Windows can reserve as much as 12 percent of your hard drive for System Restore.

If you find yourself low on space, you can reserve less space for System Restore. In XP, click Start and Control Panel. Double-click System and select the System Restore tab. Under "Disk space usage," move the slider to the left. Three to five percent should be enough.

System Restore is not a substitute for a backup. If you delete a personal file, System Restore will not recover it. Conversely, if you have to run System Restore to stabilize Windows, it will not delete or change personal files.

Windows 98 does not include System Restore. But its Registry Checker utility, also known as ScanReg, keeps old copies of the Registry. If your system is unstable, the problem may be there. To use it, go to DOS (Start, Shut Down, Restart in MS-DOS Mode). Type "scanreg /restore" (without the quotes) at the prompt. Pick a date from which to restore.

Third-party programs also can be used. Two are GoBack ($39.95) by Symantec (www.symantec.com), and CPR System Health Suite ($45) from ImagineLAN (www.imaginelan.com).

Reach Kim Komando through www.komando.com.