if you are running win xp or win 2000, you can use "erunt" to backup the registry.. i am using it, and it has worked well, for me..
http://www.larshederer.homepage.t-online.de/erunt/
however, i am confident that the regcleaner in jv16pt2005 build 1.5.0.277 (the latest release, which can be downloaded from macecraft) is safe..
if you are using win 98se, it has a reg-restore feature, built-in.. not to mention that win xp has a system restore feature..