updating the bios is pretty easy, so dont worry to much about it

im not a big fan of the updates that you run under windows (to many chances for something to go wrong)
i prefer the boot disk method
1. create a boot disk (one that will boot you to a dos prompt)
2. copy the 2 files you download from asus onto the boot disk you already created (one file is the actual new bios, the other is the utility to flash it)
3. boot with the disk, at the A: type in the file name of the flash utility (usually something like awdflash.exe) then hit "enter" and it should start up
4. once the program is running you tell it to update your bios and give it the file name of the new bios file you downloaded
5. let it update the bios (takes about 20 seconds) and do not poweroff while its happening
6. when its done it will ask you to reboot... so reboot (and pull out the boot disk)
7. when the system first starts up after the flash is complete hit "delete" (or what ever key is used to get into bios) and the select the bios option to "restore default settings"
*edit to add*
actually step 3 and 4 are much easier if combined
say for example your flash utility is "awdflash.exe" and the bios file is "bios.bin"
then at step 3 at the A: you can just type in "awdflash.exe bios.bin" (but dont use the " " ) when you hit enter it will go right to step 5 and start flashing