A computer's power source (also known as a power supply unit or a PSU) is responsible for providing sufficient power to all of the drives and components that are installed in the computer. If the power supply isn't able to provide enough power, none of the components will operate to their full potential and the computer's performance will suffer. Acer Aspire desktops ship with a PSU that is powerful enough to keep the computer's stock components running properly, but if the computer is upgraded then the power supply may need an upgrade. Upgrading an Acer Aspire's power source should only take a few minutes, with a single screwdriver being the only tool that you will need.
Shut down the Acer Aspire desktop, then unplug it.
Press the power button on the front of the Aspire's case to make sure that all of the power that is currently held in system components has been discharged.
Remove the screws or thumbscrews that hold the left side panel of the Aspire's case in place, then slide the panel back to remove it from the computer. You should have clear access to the computer's internal components.
Lay the Acer Aspire on its side with the open left side facing up. Carefully unplug all of the power cables that originate from the power source; cables should run to the motherboard, every drive, and possibly to graphics cards or other expansion cards as well.
Unscrew the screws on the back of the computer that hold the current power supply in place. Set the screws aside.
Remove the current power supply, being careful not to hit internal components with it as it comes out of the Aspire's case. Temporarily remove memory sticks or fans, if necessary.
Insert the new power supply, avoiding internal components as you position it in the portion of the case that was previously occupied by the old power supply.
Use the screws that you had previously removed to secure the new power supply. Once it is secure, begin plugging in the various cables to the motherboard, drives, and expansion cards in your Acer Aspire.
Replace the left side panel. Plug the computer in using the cord that came with the new PSU, then reboot the computer.
Beware of static electric discharge while working inside of your Acer Aspire desktop. Keep in contact with a metal portion of the case to prevent accidental discharge.