Cleaning Up the Registry - risks & prevention

[PsichoDM]

I'm contemplating cleaning up my registry by using one of the programs one can dl and try from download.com, like Registry Mechanic for example.

I know for sure that doing that kind of procedure involves the risk of screwing something up in the registry that would make the OS or certain programs unusable. Hence the question: how does one backup the registry and makes sure that it is possible to 100% restore whatever registry data was out there before one of the "cleaning" programs processed it?

Thanks!

[drizzt81]

I am using an older version of registry first aid and it makes a full backup as well as giving you a 'risk assessment' when deleting entries. I have not had any major problems that I have found at this point.

[digital_exhaust]

CCleaner.
http://www.filehippo.com/download_ccleaner/

Free, works, and has a backup option you can use before making any changes.