I have been using Ccleaner forever! It was recommended by Leo Laporte way back when he was on ZDTV long before his TWIT podcast fame. This program has always been great. One sees it recommended everywhere!
A couple words of caution/care!
First, CCleaner is for the general public. It does not take into consideration people who do graphic design, like me, and collect fonts. Check every time you do an update that something YOU want kept is not going to automatically be deleted. I found this out the hard way.
Second, be careful what you delete in the registry area. Usually CCleaner is right, but just check.
Also, do check each registry section separately and when you use the option to do a back-up of the deleted registries keep CC's name (because it has the date), but add a small note so you know what was deleted. This will make it easier to know what was in it should you want to add it back. Go back and delete unwanted backups after a while so they don't take up space.
Piriform is a software company located in London, UK. They offer great and useful software. Their products are CCleaner (cleaning and optimization tool), Defraggler (defragmentation tool), Recuva (data recovery tool) and Speccy (system information tool). All of them are free of charge, contain no malware and have cool names. ;)