Lately, I've had this problem with utorrent. I always got the error "disc overloaded 100%", while I still had about 80 gb of free space. My hdd seemed to be working just fine otherwise, so I figured that the problem would be with utorrent itself. After searching the internet for a solution, I found the right disc cache settings to solve the problem. But when utorrent released a new version, the settings went back to default and I couldn't find back the settings that had worked before.
So after a while of trying things out myself, I think that I found the right disc cache settings back. So I'm putting them here, in case that I lose them again some day or maybe I can help someone else with the same problem. :)
Oh, I also defragmented my hdd right after I applied the new settings. And restarted my laptop. So that might also have something to do with it.