I'll assume you're in Vista. This will apply to XP also, but I'm not in front of my XP desktop to give exact button pushes.
Open Control Panel
Click System
Click Advanced System Settings
Click Advanced tab
Click Settings button under performance
Click Advanced tab
Click Change under Virtual Memory
I keep a small page file on my Windows partition to aid in debugging in case of crash. I have a minimum of 256mb and maximum of 512mb. My main page file is on my backup drive and it has a custom size of 3069min 3069max.
Resize the page file on your system disk to a small amount for error logs, you need 256mb min. Then put your main page file(of whatever size you like) on your second drive, then reboot to set. If you move your page file make sure it's on a separate physical disk. Moving it to a different partition on the same disk will hurt performance.