PS is murdering my PF Usage

Not sure if this is normal but when I run Photoshop on my laptop my CPU Usage is 0%, but my PF Usage stays at 315mb and often shoots all the way up and sustains it for a bit. And it kills my ability to use any other program when it is open. Laptop specs are HP ZE5200 2.8ghz 512ram, 64mb ATI vid card.

I have a 40gb hdd, of which there is 20gb left.

please help.