Removing The Old Power Supply
Now that all power cables are disconnected, it is time for you to remove your old power supply, by removing the four screws that fasten it to the case. You will need to hold the power supply with one of your hands while removing the last two screws, as shown in Figure 12.
After removing the four screws, slide your old power supply to the front of your computer case, as shown in Figure 13. After that, you will be able to remove your old power supply from your computer.