This would appear to be your board:
http://h10025.www1.hp.com/ewfrf/wc/d...dlc=en&lang=en
To enter BIOS setup, start the PC and press the F1 key as the PC boots.
Look for a setting such as:
Skip DDC Monitor Detection
The uninstallation of previous graphics drivers is crucial.
Perhaps try this Driver Cleaner:
http://www.drivercleaner.net/