Asus P4BGL-MX - Manual (Page 36)

2-6 Chapter 2: BIOS Information
6. When prompted to confirm the BIOS update, press Y to start the
update.
7. The utility starts to program the new BIOS information into the Flash
ROM. The boot block is updated automatically only when necessary.
When the programming is done, the message “Flashed Successfully”
appears.
8. Follow the onscreen instructions to continue.
DO NOT turn off the system while updating the BIOS. This may cause
boot problems. Just repeat the process, and if the problem persists,
load the original BIOS file you saved to the boot disk. If the Flash
Memory Writer utility is not able to successfully update a complete
BIOS file, call the ASUS service center for support.