HP P Class 450/500/550/600/650/700/750 Reference Manual page 65

NOTE Setting Switch 10 to the Closed position also enables the MaxiLife firmware
'crisis' block if the power cord is unplugged (after approximately 10 seconds).
In this case, the LCD status panel is not available and the screen is blank.
Updating the system ROM
The System ROM can be updated with the latest BIOS firmware. This can be downloaded
from HP's World Wide Web site:
To download a BIOS upgrade, connect to the HP Web site and follow the on-screen
instructions to download the flash utility programs.
Before updating the System ROM, it is necessary to disable the "PSWRD" switch on the
system switches (SW-7), and to type in the System Administrator's Password when
starting up the computer. The PCI and PnP information is erased in the process.
Do not switch off the computer until the system BIOS update procedure has completed,
successfully or not, otherwise irrecoverable damage to the ROM may be caused. While
updating the flash ROM, the power supply switch and the reset button are disabled to
prevent accidental interruption of the flash programming process.
Chapter 2
http://www.hp.com/go/visualizesupport
System Board
Devices on the ISA Bus
65