Powering off your PC and associated peripherals from the mains will eliminate standby power usage and save you some money. It also reduces the PC's exposure to mains-borne surges and may prolong power supply life.

However, a recent email from one of our readers points out that when powered up from the mains, all late-model PCs simply enter standby, or "soft power" mode. You then need to push the front-panel power switch to boot up. Not content with having to perform this extra step, he went on to describe a simple means of "pushing" the button electronically, so that his PC powers up as soon as mains power is applied.

Fig.1: a 470μF capacitor and a 100ω resistor connected to the front-panel power switch are all you need to make your ATX computer boot as soon as mains power is applied.