Dear all, I have just got a refurbished 2.8 Octo from Apple. I was glad at the first minute as it comes with an expected 16M-cache 500G HD (instead of 8M-cache 320G), as well as airport extreme card installed without additional charge. But at the same time I find out that both hard drive bays 3 and 4 are not working when I connect another three 3rd-party HDs to the machine internally. While at the same time, the original HD in bay 1 and bay 2 (which is hosting one of the three 3rd-party HDs) are working properly. Is there anything I have ignored and I should perform now to enable bay 3 and 4. Or, should I call Apple now to claim a DOA and request a replacement? Thank you all very much in advance. PS: all these hard drives are working well if plugged into either bay 1 or 2.