Is the Superfetch service enabled?
It WAS disabled but I re-enabled it when I looked into this thread 1st time when I had the crash with mydefrag. I'm not sure if it's that beneficial feature on a games box with lots of memory, I just tested if turning it off made any difference either way, which it doesn't seem to.
Interestingly superfetch service was in fact not started althought it was set to "automatic". Possibly something to do with this problem. Started okay when manually run, thought.
Edit: Oh, all right. Now that I force-started superfetch, it populated the prefetch folder.