You must have the hidden and system files set to view. Recycle.bin, is fairly descriptive, Boot is the boot folder needed for booting, and Recovery is probalby an extra folder placed there in case of a system problem.
If you're going to use CCleaner, make sure that you have a full backup of your C: drive first.
I ran that program twice, over several years and both times it trashed my OS so I couldn't even boot up again.
I had to do a full C: drive restore with Ghost to get my drive back.