Depends on the OS. I can't speak for vista, but with windows xp. I have a video card with two ports. I have two 22 inch pluged into them and I use set them to vertical span in nvidia settings. This basically extends your desktop to both screens, without lag and all. It makes it one huge monitor and as long as you use some sort of maximizer ie innerspaces/keyclone etc. You can set each instance of wow or whatnot to fit the screen in any way you want.

For example i have one wow normally full screen on one screen and then i have the other 4 I run split up on the 2nd.