What is the best way of setting up a machine to utlize Photoshop's scratch disk feature. I am using Photoshop CS2 with a machine with three hard drives.
Pick your fastest internal drive. If they are all similar then go with the first partition of the OS drive.
If you are running the second two drives in a raid then use those. Basically the idea is to put photoshop's scratch location on the fastest disk or partition.