Your scratch disc space (empty space on the hard drive) should be 3 to 4 times the amount of actual memory you have in the computer. I suggest more. I like to keep 10 to 20 gigs free for scratch disk space since Max also uses virtual memory. Photoshop uses a HUGE amount of space for virtual memory. It has to keep track of not only the graphics you're working with, but the entire history of that graphic.

If you have a slow hard drive, Photoshop is going to be slow. One thing you might try to speed it up is to defrag your hard drive. This will give you large blocks of empty space for the scratch disc instead of it having to maze it's way all around the little split up blocks of data.

Talent is God's gift to you. Using it is your gift to God.