I come to the same conclusion as de Silentio.
Solutions Windows XP has a small guide from Microsoft you can find
here. All XP and below all use the same instructions. Vista has a guide
here.
For Macintosh OS X (Apple), resolution settings are found by clicking the Apple Menu, and then selecting System Preferences and then Displays. Or you can click on the Apple in the Dock at the bottom, and select Displays. Guess you won't be using Linux.