HP ProDesk 400 G1 Maintenance And Service Manual page 216

4.
Locate, press, and hold the CMOS button in for five seconds.
NOTE:
button will not clear CMOS if the power cord is connected.
NOTE:
Illustrated Parts & Service Map (IPSM).
5. Replace the computer cover or access panel.
6. Reconnect the external devices.
7. Plug in the computer and turn on power.
NOTE:
that configuration changes have occurred. Use Computer Setup to reset any special system setups
along with the date and time.
For instructions on Computer Setup, see
206 Chapter 10 Password security and resetting CMOS
Make sure you have disconnected the AC power cord from the wall outlet. The CMOS
For assistance locating the CMOS button and other system board components, see the
You will receive POST error messages after clearing CMOS and rebooting advising you
Computer Setup (F10) Utility on page 137.