I have an Optronix OP-K9A200G-MLF motherboard which was working OK.
It now says:DISK BOOT FAILURE, INSERT SYSTEM DISK AND PRESS ENTER.
I have swapped the drive with another IDE drive from another system, with the same result. Both will boot in the other system.
I can boot from the floppy and CD-ROM.
I have disconnected the SATA drives, CD-ROMs and floppy, and removed one memory stick at a time. No change.
I have tried using the other IDE port and changed the IDE cable.
Lastly I have bought a new (identical) motherboard. Still the same.