I discovered these in a list and, oddly enough for their unusually huge size, these are PATA drives so they might be a good choice when everything BUT the HDD can be kept with an older PC.

These two are DeskStar 7K1000 drives with 750 and 1000 GB capacity.

However, google'ing for these drives will, unfortunately, only bring up lots of foreign-language links (80 percent of which are in Japanese) and absolutely no auction items. So were these drives ever sold to the public or have they always remained in prototype state to this day?