This guide will demonstrate removing the computer's power supply.
Place the case on its side.
Locate and remove the two 13.1 mm thumbscrews.
Slide the side panel towards the back and remove.
Locate the power supply in upper-back corner of the case.
Remove the two power cables from the motherboard.
Remove the power cables from the CD/DVD drive and hard drive.
Locate and remove the four Philips #0 8.9 mm screws on the outside of the case.
Gently remove the power supply from the case.