alright, well where to start......
1) first up, you said that you tried perfdorming a Xenium OS recovery, what did you mean by 'flipped the switch on the mini-front panel'.
in this instance, because you cant boot XOS to use the recovery option, you need to pull the box apart and physically move the recovery switch on the edge of the chip. The switch is in recovery mode when the sliding tab is toward the top of the chip. Also, did you put a recovery.bin file in the root of your E drive before the troubles began? if not the only way the recovery can work is if you make a recovery disc with the recovery.bin file on it for the chip to find.
2) did you make sure that you set the Maxtor drive back to cable select when you had finished the HDD upgrade?
3) since you're using the solderless adapter, can you confirm that all 5 LEDs on the SP adapter light up when the chip is not installed, and that LED 4 no longer lights up when the chip is installed?