CCleaner registry option is very good but be careful! If you are not sure whether to delete something it is better to leave it. Of course CCleaner has an option to make a backup to the registry before making any changes but beware that may not help you if you deleted something way down the line. I recently had to restore my system to it’s factory condition as i was having loads of problems at startup. Tried everything, it would fix temporarily then the problem would re-occur. This could have been down to virus/malware as it usually happened 1-2 days after visiting certain websites(neither Avast nor MBAM found any) but i also suspect that i may have caused the problem by deleting an important registry file. I restored the registry using CCleaner but still no joy!

My advice would be if your system is not running slow just stick to using CCleaner for junk windows and application files. When it comes to anything with the registry files be very careful indeed.