Best Registry Editor for FREE

While its not a reg editor ccleaner will scan the registry and report broken entries and if you elect to remove them. It may not solve the issue but it may reduce the amount of manual editing.

I have used it for years and its never caused me a problem.

CCleaner here as well

I use to make good money fixing people's systems after they used CCleaner.
Could be that they already had issues that they were desperately trying to fix - but on the other hand when you find a gun in the end user's hands and he's already shot off both his feet it doesn't take a lot of imagination to guess some of what happened.** 
Now that I'm more corporate service oriented I don't see it as much, hopefully it's gotten better.
 
**side note
I learned early on never to bad mouth the previous tech.
People would often say the previous tech tried to install this or fix that - the previous tech often turned out to be either themselves, a close relative (such as husband), coworker, friend or even their boss.