For the 1959 BIOS build, press [down] 4 times, [a] once, [down] once, [a] once, [down] once, [a] once, then restart xbox. It would be nice if Xecuter released a NTSC and a PAL version of the bios so that if you are NTSC and you reset the settings to default you don't have to look up the button sequence. Crazy europeans with their PAL TV's...
btw, use the search button next time.