Replace your PC's heart: How to install a power supply in your computer
This means that two or three years after buying your computer, you may find yourself with a perfectly functional desktop that one day decides either not to power on or to emit a puff of black smoke. Upgrading your graphics card can also push your PC's power supply past its limits, depending on the model.
But fear not. Replacing a power supply is a surprisingly easy process.
How to remove your old PC power supply
The first thing you'll need to do is gather your tools--likely just a pair of gloves and a Phillips head screw driver--and remove your old power supply.
Start by unplugging from the wall all of the cables connected to your computer. If your power supply unit (PSU) includes a power switch accessible on the rear of your PC, flip it to the off position, and then remove the side panel of your case so you can access the PSU.
A number of different power connectors lead from the power supply and power the different components in your computer. You will need to disconnect all of these cables before the power supply can be removed, or else they'll snag and hold the PSU in the case.
You may find it helpful to photograph which power cables went to which components so that you can have a reference for plugging in the cables on your new power supply. Don't forget to remove the four- or eight-pin CPU power connector located near the CPU socket on the motherboard,and the 24-pin power cable connected to the motherboard along its mid-line on the left side. As you remove each cable, pull it out of the case to avoid tangling them with the other cables. Doing so also helps ensure that all power cables are disconnected, and makes it easier to remove the PSU from the case when you're done.
You'll next need to remove the screws that hold your power supply in position. In most cases there are only four screws, but designs differ from vendor to vendor. Set these safely to the side.
Now you can finally pull your old power supply out of your case.
How to replace your PC power supply
Choosing a replacement power supply can be a daunting task, but PCWorld's guide to choosing the best PC power supply can put you on the right track. Another helpful tool is the wattage rating listed on the side of your old power supply.
You can use these two tools to understand how much wattage your new power supply will need to deliver and which features you'll want--unless you're upgrading to a new, more powerful graphics card that demands a new, more powerful PSU. Keep in mind that there's nothing wrong with buying a power supply that provides more power than you actually need, especially if there's the possibility of further PC component upgrades in your future.
With your new power supply at the ready, insert it into the exact same position that your old power supply occupied. Reuse the screws that held the old power supply in position on the back panel of the case to do the same thing for your new power supply.
Next, you have to connect the internal power cables from your new power supply to the rest of your computer. Plug the 24-pin power connector into your motherboard first, then go for the 4 or 8-pin CPU power connector. Plug in the optical drives, SSDs, and hard drives. Finally plug any required PCI-E power connectors into your graphics card, then double-check all of the plugs to make sure they are securely seated. If you took photos of or labelled the cables on your old power supply, you can now use those as a reference for figuring out how to connect the cables of your new power supply.
Seal your computer's case back, plug everything back in, and power your computer up. Now you've got a PC that's ready to run for years to come without issue--or at least without PSU-related issues.
Buying a boxed, pre-built desktop is a great way to pick up a computer on the cheap. Knowing how to fix simple issues like a dead power supply is an even better way to get the most out of your money and to avoid splurging on a whole new computer.