HP Compaq Presario,Presario F500 Maintenance And Service Manual page 35

NOTE: These steps also clear CMOS.
Shut down the computer. If you are unsure whether the computer is off or in Hibernation, turn the
1.
computer on, and then shut it down through the operating system.
Disconnect all external devices connected to the computer.
2.
Disconnect the power cord.
3.
Remove the battery (see
4.
Remove the real-time clock (RTC) battery (see
5.
Wait approximately 5 minutes.
6.
Replace the RTC battery and reassemble the computer.
7.
Connect AC power to the computer. Do not reinsert any batteries at this time.
8.
Turn on the computer.
9.
All passwords and all CMOS settings have been cleared.
Battery on page 29).
RTC battery on page 34).
Preliminary replacement requirements 27