You will need to refer to your manual to update manually.
Download the latest BIOS file from here:
ASUSTeK Computer Inc.-Support-
Then as per the instructions in your manual - make a DOS startup disk
Rename the downloaded file: a8n32-b.bin or whatever it says in your manual
Save this file and the BIOS flash tool (on your mb cd) to another floppy. Follow the instructions as per your manual and you shouldn't have any problems. You may also want to backup your existing BIOS onto floppy as well in case you have problems.