HP Model 712/100 - Workstation Handbook page 109

3. Pull the power supply button straight out until it disengages from the power
switch, as shown in Figure 5–23. To allow easier installation of the new power
supply, attach the power supply button to the power switch on the new power
supply after you install the power supply into the system unit.
CAUTION: To prevent damage to the ac power cable, make sure
the cable is secured between the side of the system
unit chassis and the tabs on the bottom of the system
unit.
Field Replaceable Units 5–33