I always run a two-drive PC
system (no apologies to MAC users!). I currently have two 40gb drives, but by next weekend will have a 40gb and a 120gb. I keep all my apps on the smaller primary drive, and all the images and data on the second drive (not counting images stored on CD). It makes it easier to back up, and find stuff. For a few programs' data (Quickbooks, my PIM, my stock database) I back up to a computer offsite, but having all the data in easy to folders on the same drive makes it simple. Also, while you're not using that drive (websurfing, bookkeeping, etc,) it can go to sleep.
One suggestion though. You might make a partition of 5-10gb on the primary drive just for use by the Photoshop scratch disk. This makes PS work a little faster.
Andy Pearlman Studio