Does anybody know of a solid free registry repair/cleaner program?

You should always backup your Registry before working on it.

You can easily end up changing and/or removing more than you wanted to have happen.

"Generally" it is thought that "automated cleaning" the registry provides very little in the way of improved system performance...
And at the same time the automated process can be a high risk to your machine's functionality.
Therefore, it is not often recommended for the average user.

Know what you are changing or removing BEFORE you click to have the changes made.

Ccleaner "issues" is thought to be reliable
and
http://forums.whatthetech.com/RegSeeker_t104230.html

Be Careful.

A program I use is called Ace Utilities, but be warned with a program such as this could cause some harm if not used right.

http://www.acelogix.com/

The other program that I use is what listed above CCleaner

http://www.ccleaner.com/

Like Doug said, "Generally" it is thought that "automated cleaning" the registry provides very little in the way of improved system performance... And at the same time the automated process can be a high risk to your machine's functionality.
Therefore, it is not often recommended for the average user.

Know what you are changing or removing BEFORE you click to have the changes made.

As "Doug" said, it isn't a good idea really to just run a Registry Cleaner, unless you have a reason to. It doesn't improve performance, and can potentially damage your system. The cons outweigh the pros

I had never had problems with it, but after reading articles about registry cleaning, I stopped doing it. There was one friend who i recomended CCleaner to for the temp files made by his games, and he ran the registry cleaner just once and it crashed his computer. (Something to do with it dereferenced any hidden folders thinking they weren't there, which just pretty much kills the OS.