The chipset drivers are up to the latest versions. Checked several times.
I would agree with it being too full, but I don't believe 20GB free space would cause this much of a problem. Also, it has done this to me even when the drive was only using 60GB.
I clean and trim/defragment my drives very often, extremely anal about that, actually. So that's not the issue. I don't even store my media on that drive. Just too many large programs.
Using CCleaner is pointless in any cleaning attempt. To be completely honest you should stop suggesting that as a worthy tool. It does nothing to boost performance.