Not sure how it will be received on these forums, but have you tried CCleaner? I have gotten some disappointing results from the Windows tools like Disk Cleanup and Defragmenter, and am much more satisfied with both the performance and options of the Piriform counterparts (CCleaner and Defraggler).
I think that when you empty certain caches you may have to either do a refresh or restart explorer. I could be wrong tho, maybe one of the guys on here can get you sorted on that matter. I don't see much point in emptying something like the thumbnail cache though. Windows is just going to re-create it lol, as soon as you see those thumbnails next.