The registry has been around since Windows 3.1. Here's a classic tip from May 2000 that shows one way to keep it straightened out along with some updates and further discussion about the registry.
The registry was first introduced towards the end of Windows 3.1 as a way to central manage configuration changes and get away from the endless .INI files that plagued the Windows 3.x environment. The problem has always been how to manage the registry and how to keep it from becoming corrupt.
Today's Classic Tip comes from TechRepublic's Windows 2000 Server Tip TechMail dated May 4, 2000 and concerns RegClean 4.1a:
======================Today's Windows 2000 Server Tip REGCLEAN TO THE RESCUE
The classic utility RegClean is back for another bout with registry
clutter in its latest iteration, version 4.1a. Probably one of the
easiest utilities to use (just download and run), RegClean crawls
through your registry to identify and remove entries that are no longer
represented by an installed application or other registry-based
setting. You can read more about RegClean in Microsoft Knowledge Base
The Microsoft document contains a link where you can download the self-
extracting archive, so go get it. Once you have it, run it. It's that
simple. When the utility is finished, it'll present you with a choice
to quit or to let it fix detected errors. Go ahead and let it fix them.
You won't have to feel bad if you think it's bungled something
important. That smart little RegClean creates a clickable Undo file
that'll put everything back the way it was.
Unfortunately, the URL in that tip doesn't work anymore. You can still get RegClean 4.1a however from CNET's Download.com. Don't run and download it though if you're running anything newer than Windows ME. Even though that tip appeared in the Windows 2000 Server TechMail, Regclean 4.1a wasn't designed for anything post-Windows 9x.
The registry cleaner/repair tool I use most often is CCleaner. There are other options and tools around, but this works with Windows 2000, XP, Vista, Server 2003 - just about anything I've thrown at it. So far and I've been lucky and it hasn't cause any problems.
Even if the tip URL isn't valid anymore, the basic concept is. Occasionally you still need to do things to the Windows registry to keep it tuned and to get the junk out of it. Some people claim that your registry doesn't need to cleaned. I don't buy it. I've seen too many machines that have had problems or run too slow to start, but when you run a cleaner on them, the results are night and day.