I am never going to get on top of editing the reg. (or writing code etc) and wonder if registry repair programs are worth using. Like, 'Free Registry Fix' just found 600 errors, do I auto fix 'em?
The registry is a tricky thing. I wouldn't trust any automated program to touch it, especially since that program doesn't have a clue what all the other software installed on your computer intended with their registry entries.
Far better to find specific solutions to specific problems. Why do you think you need to fix your registry? What isn't working right?
After years of installing and removing trial programs and other wear and tear, the registry can get lots of junk accumulation. It makes sense to try to tidy it up.
However, there are many registry repair programs out there, and some of them really trash things. My suggestion is to first do an image backup of your system, so that you can go back to exactly as it currently is, if something goes terribly wrong. Then Google some articles on the subject, giving more weight to articles in major magazines such as PC or PC World.
In my own experience, I have found that cleanup programs from places such as Norton are fine, while other programs are too aggressive, requiring the use of that image backup.
I use Ace Utilities. It has a duplicate file finder and also a utility that lets you see how much space is being taken by each folder and, as you drill down, how much space is taken by each file/folder in that folder. You can find broken shortcuts, get rid of broken uninstall settings, completely wipe data from your disks (so that can't be recovered by undelete programs), and it has a registry cleaner.
As already stated, most registry cleaners can be too aggressive, and this is no exception. Do NOT use any registry cleaner on automatic. ALWAYS do a backup of the registry before proceeding. System Restore is an easy way to do this. Finally, you have to commit the time to look at each delete candidate manually and decide whether to kill it or not. You have to make sure it belongs to something that is no longer on your system. You have to be careful because some programs may have been deleted, but the company that made them also may make subcomponents for other programs that are still needed.
You can back up the registry before trying the fix-it utilities. Start regedit and then click on My Computer at the top left tree and go to File | Export...Give it a name and then select All for the export range.
You can then import the saved registry if something does go wrong. However, anytime you mess in the registry expect the worst and be ready to start from scratch (full system reload) if it goes bad.