It's said that two heads are better than one. So why not test that adage out with an old computer you have sitting around the house? It's an easy and cheap trick these days for the many homes that have old computers collecting dust and cluttering closets. Special switches can connect the old PC, or CPU, to the same monitor and keyboard that's being used by your newer computer. They make it easy to flip back and forth between, say, a computer used for work and another for play.

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Once the expensive tools of IT pros, so-called KVM switches (for keyboard, video and mouse) can now be purchased for $30 or less online or a bit more at local stores like Circuit City or Best Buy. I've used a switch from a company called Raritan for years without a glitch. Other makers include Belkin, IOGear, and Avocent. That price includes two sets of cables to connect the PCs to the switch, which then uses your existing cables to connect to the monitor, keyboard and mouse. For a slightly higher price, you can get a switch that also will connect both PCs to one set of speakers—or for the glutton, connect four or more PCs to one set of controls. Some of the KVM switches only connect keyboards and mice to PS/2 ports, a common connector on Windows PCs. Some connect keyboards and mice that plug into Universal Serial Bus ports, and many of those can switch between Windows PCs and Macs. Be sure to check that you get the KVM switch type that matches your computers.

To switch between computers, just push a button on the box or hit a special combination of keys. It makes it easy to keep one PC for a dedicated purpose, perhaps as a media player (or in my case, for testing software) and the other for general use. Or in a family, keep the kids' games off the machine used for balancing checkbooks. Some KVM users bring a notebook home from the office and connect it to the home PC's monitor and keyboard.

There is, of course, a downside to all this. The second PC only takes a bit of space under the desk—but it triples the cable spaghetti down there. Take time to mark the cables, or you soon could be losing your head.