You are correct in sense, the d0 has to be connected.. but you have to remember, it has to be connected to something that is part of the xbox motherboard (in such case a ground is what tells the xbox to boot to the lpc port) from in your mind, you have the idea if your d0 is soldered to a brick, it will boot any chip you stick in there.
What you need to do, is just put each chip in, and at the same time, ground out that d0 wire (you can just hold it to the side of the case next to the power supply (just dont touch anything else on the circuit board)
