When you use one keyboard and mouse to control a Mac and a Windows computer at the same time, you may have to deal with a few quirks.
Macintosh keyboards offer different keys than PC keyboards, so although using a Macintosh keyboard on a PC works relatively well (since few people use the Windows-specific keys on many PC keyboards), the converse is more problematic. First, PC keyboards lack the Power key, which means you have to use the power button on the Mac, and you can't use Apple's MacsBug debugger. Second, the main modifier keys on a PC keyboards are, from left to right, Ctrl, WIN, and Alt, as compared to the Mac's Control, Option, and Command. You can swap the WIN and Alt keys to match the Mac's Option and Command keys using ResEdit on a backup of your System file (see http://www.resexcellence.com/12-27-99.shtml for instructions). Alternatively, if you use a Microsoft Natural Elite keyboard, Khalid Shakir has made a free driver available, and Manual Labor is working on a driver for the Microsoft Natural Keyboard Pro ( http://www.mit.edu/~kshakir/msnatural/ ).
The situation is better for pointing devices like mice, thanks to Alessandro Levi Montalcini's powerful $20 shareware USB Overdrive, which lets you use multiple buttons and scroll wheels on almost any USB pointing device with the Mac OS ( http://www.montalcini.com/overdrive ). The reverse-using a Macintosh mouse on a PC-is dependent primarily on whether Windows recognizes the pointing device and can load an appropriate driver.