Chris wrote:
  No the CUDA switch is a button. Don't go jumpering
unknown wires (not
 that you planned to I am sure). I just popped the top on an LC 2, no
 switch. So there may not be one on the 476 either, I would verify, but
 both my 475's are in use at another location. 
I have a couple of 475's with the same symptoms so I am follwoing this
thread carefully. My 475 has no button, red or any other color that I
can find.
  So you would press Command-Option-P-R. Hold these down
right after
 hearing the startup bong, and continue to hold them until you hear the
 Mac bong again. It is recommended that you do this until it bongs 3 times
 total (just keep holding them down). I don't know exactly why, but that
 is what Apple's TIL suggests. 
Being an Apple newbie, what is TIL and where can I get one?
   -- hbp