Replaced logic board now it doesn't boot past grey screen

I bought refurbished logic board that was said to have come directly from Apple as surplus. It looked great in original Apple bag. I installed the board and before I put the top case down, since it is the most difficult part of the process, I put in memory and the battery and pressed the power button. I got the bong sound from boot up but it just sits at a grey desktop. I don't get the Apple symbol and it does not come up.

Is there something else I have to do? Do I need to boot from the install DVD the first time? IF so what are the keyboard commands to do that I can't seem to get the right ones for this powerbook.

Any help is greatly appreciated.