|Oh yeah,that's right, pure dos--even 98 dos--will only see files in 8.3 format.|
Since you appear to have the necessary boot files we can try setting up the flash drive to run the update by itself.
I assume you downloaded the most recent update file--P5GC-MX-ASUS-1333-0413.zip--and flasher file--AFUDOS236.zip--and extracted them and copied them to the flash drive.
You need to rename the update file on the flash drive so it complies with dos 8.3 format. Your example will work fine so rename it from
P5GC-MX-ASUS-1333-0413.ROM to P5GC.ROM. (Sometimes when you rename files you unintentionally get a doiuble extension so take a good look at the renamed file and make sure it's just P5GC.ROM and not P5GC.ROM.ROM.)
Then use NOTEPAD and write in it a single line exactly as:
Save that file as AUTOEXEC.BAT on the flash drive.
So the only files on the flash drive should be the two hidden dos boot files--io.sys and msdos.sys--as well as command.com, afu236u.exe, p5gc.rom and autoexec.bat.
With that, the drive should be ready to go. Autoexec.bat will run on it's own and give the command to do the update. Now it's possible part of the update process will ask something like 'are you sure you want to do the update' which of coiurse will require a keyboard response.
If that happens shut down the computer and remove the flash drive and put it in the working computer. Run notepad again and open the autoexec.bat file on the flash drive. Edit the line from:
AFU236U /iP5GC.ROM /y
Adding the /y is sometimes seen by the command as answering 'yes' to its built-in question. It may or may not work in your case but give it a try if you are asked the 'are you sure' question. If that doesn't work then we'll have to find a flasher that is compatible with the bios chip and won't pause to ask questions.