A power surge can seriously harm your computer. Fortunately, the computer's power supply is built to take the brunt of any power fluctuations. If you find that your system no longer powers up after a surge, the culprit is most likely the power source. Fortunately, replacing your power supply isn't as difficult as it sounds.
Determine the type and voltage of your power supply. The easiest place to locate this is looking on the back of the power supply installed in your computer. There should be a sticker which gives information about the supply. If you don't see it there, then check your computer manual. You should also be able to find it online at your computer manufacturer's website.
Purchase the appropriate power supply online or at a nearby computer store.
Unplug your computer. Detach any USB-connected devices, printers, monitors, etc.
Open the computer case with the screwdriver. Remove the screws and set them aside.
Ground yourself by touching a large metal object. This will dissipate static electricity in your body which can damage electronic components.
Locate the power supply. It is usually near the rear of the case, where the plug enters the machine.
Unplug the power supply from the motherboard and peripherals. The power cables are usually multicolored and fit into the various drives and other internal devices by means of a socket at the end of the power cable. The power cable attached to the motherboard is usually secured with some type of tab that you have to press before pulling on the socket.
Unscrew the power supply from the case. Check the back of the case for a series of screws in the vicinity of the power plug and unscrew them. That should release the power supply.
Remove the power supply from the case.
Insert the new power supply and screw into place.
Plug the power supply back into the motherboard. Attach the drives and peripherals.
Replace the case cover and screw this back on.
Plug in the computer and reattach any external devices (hard drives, printers, etc) and monitors.
Start your computer. It should boot into the operating system as normal.
Things You'll Need
Replacement power supply
Always use surge protectors with your computers. Even better is an Uninterruptable Power Supply (UPS). Not only do these provide your computer with battery backup in the event of a power failure, but they clean up the electricity flowing through them, smoothing out any bumps and surges in power than can harm your system.
Be sure not to purchase a power supply that's too powerful for the circuit where it will be operating.