When you install, uninstall, and reinstall programs on your computer, registry keys are created, modified, and/or deleted. Over time, your computer's registry may begin to contain corrupted, unused, and unnecessary registry keys, especially if keys are not removed when you uninstall a program. As a result, you may begin to experience problems, particularly when using OLE to embed objects. The RegClean utility is designed to clean up unnecessary registry entries in your registry. Be sure to backup your PC before running regclean or any such utility. There is always a small chance your PC will not boot after running it.
I have used the utility to good effect and I know of many who also have good experiences but I have seen cases where the PC was left unstable after running the utility. These sad cases probably had a corrupted registry before RegClean was run. My best advice is to run RegClean periodically as a maintance task (best) or to run it when NT gets flaky (more risky). If you chose to run it when your installation starts having problems, it may do its magic or it may make the problem worse. You have the option of restoring what was cleaned out by RegClean [assuming your PC runs at this point.]
I have seen reports that RegClean can cause problems if you have Office 2000 installed.
The current version 4.1a of RegClean works on Windows 95, 98, NT 3.51, NT 4, and 2000. It is NOT compatible with Windows ME or XP.
A alternative may be the excellent freeware Regcleaner.
Allows you to remove software registry entries.
Allows you to remove registry entries of start up programs.
Ability to uninstall software (similar to Add/Remove Software in Control Panel).
Ability to modify the Uninstall Software list (in Control Panel).
Ability to remove file types.
Allows you to remove unused DLL files.
Semi-automatic (You select, RegCleaner will remove them from everywhere).
Automatic backup, very easy to use.
Registry cleanup feature that does the same thing those other so called 'registry cleaners' do.