Osuman and Flanigan both have valid points.
Make sure the bios power management setting match those for windows. If they differ, one will spin the drive down, the other will power it right back up. Its really agrivating.
Also, lots of little apps (ICQ, Messenger) write to the HD every time you do something. Check that out as well. ICQ in particular writes to the HD with every incoming and outgoing message.
Knutsaq.