How do I simultaneously use two keyboards?

Possible Duplicate:
How to use two keyboards simultaneously on a single computer w/windows?

I prefer to type with one keyboard per hand. In my last job, I had a setup that worked using a macbook pro and the apple external keyboard plugged into a big apple monitor which then plugged into a special non-usb port on the macbook. Now I'm using a regular monitor and keyboard, but I can't use shift across the keyboards.

For example, I want to type a capital A. I hold down the shift key on one keyboard, and i press the 'a' key on the other. The result is a lower case a. It was by far the most comfortable typing I've ever done and I want to figure out how to continue to do it.