I suspect the unwanted process is Indexing.. that will run big drives for days... seems the OS does not look at Processor usage, but Mouse or keyboard Usage for whether there is activity. Not sure if that is what is causing all your HD access, but you can check by turning off Indexing. Oddly, if you let it finish and the Drives are local, not external, it seems to clear up. I have noticed on Vista that it attempts to reindex my Network and External Drives each time I access them, so I turned it off on them.

ratscloset
aka John