Dell GX620 - 3.6GHz Desktop 1GB RAM 80GB Windows XP SFF User Manual page 84

Slide the power supply toward the front of the computer by approximately 1 inch.
5
Lift the power supply up and out of the computer.
6
Slide the replacement power supply into place.
7
Replace the screws that secure the power supply to the back of the computer chassis.
8
Reconnect the DC power cables to the power supply.
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2
1 release button
2 power supply
3 screws (4)
4 AC power connector
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4