And how to flash Backup BIOS? (using Main BIOS) Quoted from Dark Mantis
If you have a PS2 keyboarrd connect that instead of the USB version as it is more reliable.
From a cold start with the power to the machine switched off press the power button and then enter the BIOS by pressing Del.
Then when you get to the main screen press F9.
This will bring up an extra screen which will display more information about the two BIOS versions. Assuming they are different exit the BIOS and shutdown.
Again press the power button and this time press Alt + F12
where you would normally use the Del key to enter the BIOS. You will find that then your monitor will turn black and you will see:Press [Enter] to start copying main BIOS to backup BIOS...
When you press Enter more text will appear saying:Writing BIOS image.... xxxKb OK
Once completed more text will show: BIOS successfully recovered! Power off or reset system!
Do as it says. Both Main and Backup BIOS chips now store the same BIOS version. You can now reboot as normal.