I use a combo of Regseeker and CCleaner. Regseeker tends to find alot more errors, plus I like the search feature in it. It makes it much easier to clean up junk left behind from unistalls on programs that have keywords that are normally ignored by cleaners (Norton is the best example) CCleaner ads the nice ability to clean almost all temp files on the computer.
iolo system mechanic isnt free.its a trial ware
moreover it has got many other tweaking options too.
one thing that is most certainly noticiable in system mechanic is that ur internet speed increases with one of the many tweaking options available.
and the cracks can be found no doubt but the iolo ppl are quick enough and make sure that thte cracked keys are taken to their notice : wink: