How much wattage should my new power supply provide?

--Steven Zezulak, Englewood, Colorado

As a general rule, go for as much as the total of devices inside your PC require, plus 30 percent. If you're not sure, err on the side of too much. Other than price, buying a too-powerful supply has no downside, since a 500-watt power supply can run a 200-watt computer as efficiently as a 300-watt power supply can.

The power supply is one of a PC's cheaper components, but a good one is worth a few extra dollars. A power supply from a respected company such as Antec, PC Power and Cooling, or Seasonic will cause fewer problems, last longer, use less electricity, and run more quietly than a cheap knock-off will. For more details, see "Do the Math to Get Your PC All the Power It Needs."