O.k, so you are a complete layperson, has never open your computer case, is afraid of doing so, but want to replace your power supply unit with a better one. This tutorial was just made for you: a step-by-step guide on how to replace your power supply full of pictures, especially made for people who has never opened the PC case and/or is afraid of changing things inside the PC.

Why should you replace your power supply? If you don’t specify a power supply brand and model when buying your computer, the computer store will probably sell you a PC with a “generic” power supply, which is very low-end and isn’t enough for high-end applications.  Telling them the power rating you want is not enough, since cheap power supplies simply cannot deliver their labeled power rating. For example, a 400 W “generic” power supply won’t be able to deliver its rated 400 W.

Your computer may be working just fine with a cheap “generic” power supply, however when you upgrade a computer part of your computer – specially the video card – you may face stability issues if your power supply can’t deliver enough power to your system. By “stability issues” we mean your computer reseting out of nowhere, the infamous Blue Screen of Death and your computer “freezing”. Also, if your current power supply is overheating – i.e., if you place your hand on top of your computer right above where the power supply is installed and it is very hot – it is time to replace it with a better power supply.

Luckily there are several terrific power supply manufacturers nowadays on the market. Buying a new power supply (or PSU for Power Supply Unit, as it is often called) has no mystery. Select your new power rating and buy one. Any power supply unit should fit your computer nicely, but just in case you should buy an ATX12V 2.x power supply. If your motherboard needs an EPS12V connector – which is very unlikely – you will need to buy a power supply that offers an EPS12V connector. We don’t think this is your case, as only a few very high-end motherboards requires this connector, and if your motherboard does, you are probably already using a high-end power supply anyway.

Power supplies up to 500 W will do the job for the majority of users. Above that only if you have several hard disk drives and/or are using two video cards under SLI or CrossFire modes. For an overall view on power supplies including their main specs, read our Power Supply Tutorial. This tutorial may be handy when buying a new unit.

So let’s roll up our sleeves and work! The first you should do is to disconnect all your computer external cables – especially the power cable – and put it on a table. Put the rear part of the computer facing you. Pay attention on the screws located there. You will play with six screws, two located on the right-hand side that fasten the case side panel (i.e., the case “door”) and four that fasten the power supply unit to the case, see Figures 1 and 2.

How To Replace Your Power SupplyFigure 1: Screws located on the rear side of the case.

How To Replace Your Power SupplyFigure 2: Screws located on the rear side of the case, closer view.

You will need a Phillips screwdriver. Remove the two screws located on the right-hand side that fasten the case side panel and slide this panel as shown in Figure 3.

How To Replace Your Power SupplyFigure 3: Opening the case.

In Figure 4 you case our case opened and the exact location of our power supply.

How To Replace Your Power SupplyFigure 4: Case opened.

Before removing the power supply, you need to disconnect all power connectors that are installed on different devices inside the computer.


Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.