ZoomIt v3.01 by Sysinternals will allow you roughly the same screen-zoom capabilities that you have in a Linux desktop with 3D effects enabled (Compiz) or Mac OS X. It’s a nice small utility (only 129k before install!) and works in both XP and Vista.

If you use your computer screen on a live webcast or make presentations to people often using your computer, this is a must-have utility and you’ll make very good use out of it.

And yes, it’s free.

To those wondering if it has the same "smoothness" as Linux or OS X does, not quite. But it’s close and it works well.