Originally Posted By: seanog
It's retail, but also have Leopard & Snow leopard. Tried booting from all with external player.
Does the internal not work on the 20"?

The 17 and 20 use the same RAM. Maybe the RAM on the 20 needs to be reseated or maybe it's bad. I'd try reseating the RAM and/or putting the 17 RAM into the 20. Try booting from Leopard or Snow Leopard if the 10.4 installer DVD is earlier than 10.4.4, or it could be even if it is 10.4.4 on the retail they both came out the same month so maybe the 10.4.4 on the retail is not the right 10.4.4 to boot the 20. Sometimes they slightly modify the same version of the installer to be specific to the particular model.

Do the RAM thing first.