Ok, the 1001th time I post this

:
Using AMIBIOS Flash Recovery Mode to update your BIOS:
1. Copy the BIOS image you want to flash to a floppy and rename it to
AMIBOOT.ROM.
2. Insert the floppy in your system's floppydrive.
3. Power on the system while holding
CTRL+Home keys. Release the keys when you hear a beep and/or see the floppy light coming on.
4 . Just wait until you hear
4 beeps. When 4 beeps are heard the reprogramming of the System Block BIOS went succesfull, so then you may restart your
And yes, you may also press F10 key during POST in your case to perform BIOS update. Since updating BIOS this way only the system block of BIOS will be updated (the boot block part is left intact) you should be able to recover when something goes wrong during flashing process. You can just reflash your BIOS the above described way.
Last but not least, please be SURE to have the correct file for your board.
there are several 865PE based boards made by MSI and so there are several BIOS updates available. Note the difference!