I'm not a fan of Asus and won't be buying another because of having to fight Asus over a bogus warranty denial (it's a long story but they only replied about how to RMA my unit weeks later on the EXACT day the warranty expired).

Anyway, it's just a matter of hitting F9 to do this, there's no need to worry about booting from USB or CD (unless of course you want a different OS eg. Windows XP Pro, Vista/7, or a flavor of Linux or Unix).  Also remember that you need to fully/properly power off your system to do this, rebooting is not enough.  If you still don't see the BIOS Setup Prompt, you'll have to remove your battery and re-insert it.

Basically once you hit F9 the restore partition boots a version of Norton Ghost and it restores everything to the factory settings based on the ghost image sitting on the hidden FAT partition.

There is some weird quirk that Asus (at least Eee PC's) love not to let you into the BIOS except when it first thinks you are powering on.  This is very annoying if you wanted to boot from CD or USB.