HP Compaq Presario,Presario 4400 Hardware Reference Manual page 19

Computer Upgrades
Å
3–2
3. Disconnect the power cord from the electrical outlet 1 and then
from the computer 2.
Disconnecting the Power Cord
WARNING: To reduce the risk of personal injury from electrical shock
and/or hot surfaces, be sure to disconnect the power cord from the wall
outlet, and allow the internal system components to cool before
touching.
4. Disconnect all external devices connected to the computer.
Hardware Reference Guide