I'm an IT guy and build PCs. My reasons for doing this are:
a) The four drives could have their own power supply and not add extra stress to the Win7 machine.
b) They won't add any heat to the nearby Win7 computer, which already has a CPU running at about 40C.
c) Ideally, I could just turn on the box they're in when I want to access their contents.
Please note I'm not saying this is possible - I'm just asking the question to see if anyone has done a similar exercise.
Personally, I don't see how I could collect and channel the outputs from four drives in a box, unless they had their own operating system (together with motherboard, cpu, ram etc etc) to translate their outputs, in which case I might as well put them in the Win7 tower.
Come to think of it, a modification of that arrangement could be possible, like placing the four drives in another case hard alongside the Win7 machine, powering them with that case's power supply, but taking their data cables through into the Win7 case and onto the motherboard, which has four spare SATA ports.
I know it's a bit of a geeky exercise, but that's why I posted here in Geekzone, the home of no.8 wire fixups :-)