right click on the windows task bar and go to task manager, see whats using all your CPU and memory. that'll be what is making the hard disks go crackers ! post the processes up here and we'll see if we can help you out as to what they are.

Have you got any bittorrent running? i know ABC bittorrent client thrashes the fuck out of your disks and CPU, i switched to using uTorrent and its loads better