Quote from prt_systems:
Linux.
Seriously though, there are a number of issues with any registry cleaning attempt. I have written several registry cleaning utilities. Without going into the details - you dont want to know how sausages or registry cleaning programs are made ...... - my advice is to attempt to avoid registry cleaning altogether by installing a base version of the windoze OS and then installing your base applications, backing up, and then do NOT install/unistall any further software unless absolutely necessary.
Every registry cleaner has a small chance of breaking something - although in the more recent versions of the OS - XP etc - the change is reduced.