Howesy, you have no way to determine what data the OS is swapping out to disk. You're jumping to the conclusion that it's swapping out your data, but it could equally as well be swapping out code to make more room for your data.
The memory manager in Win XP is *very* mature. It's been around since the NT 3.5 days and has been written and improved upon by some *very* smart people.
If you're finding performance problems when using Photoshop, the most likely cause is simply that you don't have enough RAM to adequately support what you're trying to do on the machine. (And unless you get perfmon data, we can argue this back and forth with no resolution.)
The only control XP gives you over the pagefile is in System control panel, on the Advanced tab, click Performance Settings. On the Advanced tab, click "programs" in both frames.
You'll probably have to reboot to get those settings to take effect.