You may need a usb flash drive to update the bios. You have to download both the flash program and bios file to the usb drive. I've never had to use it, but it works. I'm surprised a bios update is even available for an hp board. There's no reason to update the bios unless the new file permits you to run a different cpu.
Since I encountered this problem I have replaced M/Bds on the same product without any trouble, so it was that one m/bd that was at fault..Thanks for your help.