not playing a game full screen (how to)

I was once walking around at this cyber cafee and I saw these guys playing WoW in a smaller box while also typing up a paper. I also saw this "how to" guide in a pc gamer on how to make your game only a little part of the screen.

I am wondering if anyone knows how to do this. Thanks!

Be aware that some games simply dont like being run in windows mode or being task switched. You'll know if this is the case if you game (or system for that matter) just locks up and requires a reboot. I wont say that it's an uncommon issue with older titles as new games still come out that done like doing either one. It's not a big deal, but I thought I'd mention it to you if your new to the scene and start to wonder why some game isnt doing what you want it to.

I dont know what specific trick or technique that guide had, but i know a program called 3D Analyzer allows you to force fullscreen games on a window. I never bothered messing around with the size of it, but i imagine you could do so very easily. The program is a free download.