Tony, congratulations, that is a SUPERB FAQ.

The reason I needed it is that, unfortunately, I am starting to get the HDD not found message too. Previous two times that happened, extracting and reinserting the empeg from/into the sled solved the problem; but last time I had to open it. By pressing back the ide cable on the mboard, and on the hdds (I have a 60Gb, 2 HDD empeg), I could access them again and now I'm backing up drive0 and drive1 one last time before I start playing with the ide cable. I noticed the problem always occurred after I had gone on some more bumpy road for a while (for those who know Rome, I am talking about the "sampietrini" on "lungotevere", i.e. the old paving you find in some parts of the riverside streets).
Amogn the possible causes, I really hope the problem is not on the ide connector on the mobo, as described in the faq. I have no soldering skills whasoever.