HP Deskpro 1000 Reference Manual page 14

3. Plug the computer power cord into the power cord connector
on the back of the computer and into a grounded outlet.
WARNING: This equipment is designed for connection to a grounded
!
(earthed) outlet. The 3-prong grounding type plug is an important safety
feature. To avoid the risk of electric shock or damage to your equipment,
do not disable this feature.
Plugging in the Computer
4. Push in the power button.
Reference Guide 1-7