A lot of the parts for the clone machines are proprietary, and computer resellers usually take the whole drive sled/rails out when removing the hard drives, and neglect to put them back before putting them up for sale. I had to buy 2 for one of my Mac Pro's, and three for the other, on account of that, and, of course, the seller didn't disclose beforehand that the drive sleds would be missing. I mean, how hard is it, really, to remove the hard drives from the sleds, before disposing of them? It's like a lot of the early Macs that have the Apple branded hard drives, with an Apple ROM on them. It's extra work to have to use a non-Apple drive, when they could just wipe the original Apple drives, and leave them in the machines. I hate when sellers do stupid crap like that, that makes life more difficult for the buyer. I bought a vintage 486 system once, where not only did the seller remove the hard drives, he removed the entire hard drive cage, and the cage is unique to that case, so I couldn't even put a hard drive in it at all, without the cage, and, again, they don't disclose these important facts before you buy.