Hmm am not quiet sure about CCcleaner or Advanced System care,they do something in registry but cant say am 100% sure it will help.Mostly time they doing great job,but also they can make mess and cause game,programs stop respond...
I can suggest him to manually delete SA:MP keys into registry but since we both know that every game making 100 or more can be really painful job,also there are plenty similar named keys so you can make worst than making SA:MP playable.
Simple as moo suggested above install game somewhere else and would be enough to avoid problems.
And Karlip i have got similar problem,nothing useful i found on SA:MP forum,people just having random ideas and no one is 100% correct to suggest Simon he can deal with SA:MP crash,or to be honest i can suggest him to make fresh installation of windows and i can guarantee 100% but that is last solution.