Run Windows on Your Mac

If you have a Macintosh computer with an Intel chip, you don’t need a separate computer to test in a windows environment. It is now possible to run Windows right on your Mac.
Apple offers the free Boot Camp, as part of the Leopard OS X release, that allows you to switch to
Windows on reboot. There is also Parallels Desktop for Mac, a commercial program that allows you to toggle between operating systems easily.

For more information see www.parallels.com.
Both options require that you purchase a copy of Microsoft Windows, but it sure beats buying a whole machine.