This is being advertised as very safe and I do trust Comodo.

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Some notes on the Comodo registry cleaner. I'm far from an experienced reviewer so here is a simple review.

Download Size: 9.01 MB
License: Freeware
Requires: Win XP/Vista

Install was smooth, no toolbar offers or anything to avoid.
GUI is very similar to the Comodo firewall.
Has a startup manager as well as many settings including scheduled scans.
You can Cleanup, Compact and Backup the registry.
It gives an option to jump to the registry key or add it to the ignore list.
Also lists unsafe to remove entries.
Automatically backs up the registry before cleaning.

Overall I like it. Very easy to use and gives a lot of information on what you are removing.

361 errors found and removed. All is well.

It would be a good idea to backup the registry before you make any changes since it's in the beta stage. I use RegSeeker. It's free, and it's good software.

It backups the registry before it cleans the errors it found from scan.
I think its much better than regseeker.

I just downloaded it, and Comodo found 281 errors. Afterward, I used Registry Mechanic (found 3 errors), CCleaner's registry tool (found 0 errors), and Regseeker (found 26 errors) so it only left a few problems behind.

It is always better to back it up yourself though, it takes all of 10 seconds to do it, after all.