The thing I cannot fathom, is how none of diagnostic tools were able to pick this up. I have since found a few articles on major updates to the way utorrent handles multiple threads since vers 2.2.1 so now I think I finally have my answer. Until I updated to the current version 3.5.4

I then attempted all of the published fixes for the Disk Overload issue - increasing the disk cache, changing some of the Advanced settings - nothing worked. That's when I spotted the 'Disk Overload 100%' error in the utorrent client footer, and that the xfer speed would drop to only a few kb/s. I was about to concede defeat and reinstall windows and start from scratch, when I noticed these issues were occuring in a sequence, and only after I had utorrent running with a fast transfer speed (approx 2.5 mb/s). Nothing worked, and none of the diagnostic tools were telling me what the issue was. There was nothing recorded in the Event Viewer logs, I rigorously tested all the hard drives, memory, a complete virus scan, uninstalled the last dozen programs and updates, you name it - installed ALL the Windows 7 available updates, removed optional add ons to the shell. The only way to get out was to force a reset. uTorrent version: Last Stable (3.3 29625) Every time I start downloading something big, or many small files (4-6Gb each), uTorrents goes in Disk Overload 100 and stops downloading anything (actually it does not stop completely, but the download speed becomes so slow that It is almost irrelevant). 2 days ago I started getting major freezes across multiple applications - Windows File Explorer, Chrome, utorrent - even Task Manager would crash and freeze. I have been running an old version of utorrent - 2.2,1 for quite some time, mainly because I believe in sticking with stable versions of software to limit the amount of time I have to work 'on' the system. Thought I would share this to save some other poor shmuck 2 days of troubleshooting to diagnose the issue.

Disk overloaded 100 utorrent 2.2.1