I recently added a second hard drive on my system.  A Western Digital  160 gig at 7200 rpm. My original hard drive is a 60 gig maxtor @ 5200 rpm.  I was indeed suprised by how much smoother fs 9 runs on the new drive.  In fact, so far all the software I installed on it runs better.  I also installed a copy of xp on the new drive as well.  Almost like having a second computer in the same tower.  Now, is the improved performance mostly do to the higher rpm of the drive or mostly to the fact it's a cleaner disk or possibly both?