I'm sorry, did you happen to check to see if the hardware is detected by ShowConfig? Does the ram show up in WorkBench?
Usually an unpowered expansion will prevent booting at all, so of the hard drive is attached does it have another power source? If yes, does the hard drive spin-up? Of course have you checked for good/clean contacts on the expansion port? Any LED flashing from the HDDs access?
If no hard drive showing up, have you unplugged it and just checked for the ram alone?