A) Do you still have the manual? I can't even find that model on asus.com - where / when did you get it?
B) If you have extreme patience, keep booting and try each key. Delete is a fairly common one for Asus - it's the BIOS key for my last two Asus mobos.
C) Is the printer a USB printer? And what is Internal USB - do you mean built-in, or is it actually internal (you have to open up the machine to access it)?
D) My best guess at the problem you are describing is that either one USB port is dead, or they are all dead (if you have more than one). A little clarity would help. How many USB ports does it have, and do any of them recognize any device, such as a thumb drive?
E) Or is the CD Rom a USB device too, which would make my USB-is-dead guess wrong?