HP EliteDesk 800 G5 SFF Maintenance And Service Manual page 105

Computer does not continue and the HP logo does not appear.
Cause
ROM issue - POST error has occurred.
"Illegal Operation has Occurred" error message is displayed.
Cause
Software being used is not Microsoft-certified for your version of
Windows.
Configuration files are corrupt.
Solution
Observe the beeps and LED lights on the front of the computer.
See POST error messages and diagnostic front panel LEDs and
audible codes on page 109 to determine possible causes.
See the Worldwide Limited Warranty for terms and conditions.
Solution
Verify that the software is certified by Microsoft for your version
of Windows (see program packaging for this information).
If possible, save all data, close all programs, and restart the
computer.
Solving software problems 95