Replacing your power supply:
[warning]You must remove the mains power (from the wall) before you begin.[/warning]
You will need to open your computer’s case, of course. With the computer facing you, the panel on the left side is normally the one removed for service. Often a manufactured PC such as Compaq, Dell and so on will have some sort of locking mechanism which must be negotiated. In these cases you will want to consult your manuals or on-line documentation. You should also check to make sure replacing the power supply won’t void your warranty. (If you are still in warranty and replacing a failed supply the vendor should provide one for you if not do the work themselves) If you plan to open your computer case for any reason you should invest in an anti-static mat. These go for around 20 bucks and will keep you from destroying parts of your computer with static electricity.

Unscrewing the Case

Sliding the case side open

With the computer open, turn the open service panel side towards you. The power supply is usually located at the top left and is normally a grey, aluminum enclosed box with fans. Unless you’ve cleaned your computer lately you may want to be prepared for a great deal of dust as this is one of the locations which accumulate it. The power supply is normally attached using four Phillips-head screws, accessed from the back panel of the case. Prior to removing these, you will need to disconnect the various internal power leads from the motherboard, hard drives, CD / DVD and elsewhere. If you are not familiar with this process you should take notes of the number / type of connections and where they are prior to removing them. Also pay attention to the way the power cables are routed; if they are arranged neatly so as to minimize the impact on airflow / cooling you’ll want to do the same with the replacement ones.

Unplugging the Devices