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They may not be as glamorous as ultrafast CPUs, humongous hard drives, or the latest 3D graphics cards, but cooling and power components are the oft-forgotten workhorses every PC relies on. If you plan to add new components, make sure your power supply can handle the added load.

Alas, some PC makers scrimp by installing cheap power supplies that can't handle varying wall voltage or voltage spikes or can't provide the clean DC power needed for long PC life. Worse, many use inexpensive "sleeve-bearing" fans that wear out in a year or so; a CPU fan failure can cause the processor to fry in minutes. Long-life ball-bearing fans are essential.

Actually, power supply failures aren't unusual. They can be hard to diagnose, but if the fan on the back of the power supply isn't spinning, that's usually a good indication the supply has expired. You can also use a voltmeter to see if voltage is reaching the power supply connectors; and PC Power and Cooling (see "The Top Down") sells an inexpensive ($9), easy-to-use power supply tester.

Even if your PC's power supply seems okay, a new one provides clean power and high-capacity cooling--and is usually quieter than the original equipment.