[Yoherz]

Ok, there's a few factors here.
For one, if they were illegally uploaded, they probably would have shut it down by now, so it's doubtful they did so illegally. This means they own it and can do whatever they wish with it.
Two, look around the site and see if they have a disclaimer similar to the one we have here on CH. If they do, then you could get in trouble if they catch you.
Three, if they don't have one, then it'll be their a** they get on for file sharing, and will probably only get maybe one of the people that downloaded things, and that's only if they can track the people downloading the material.
Four, if they ever do catch you, you can say you're friends with the person that uploaded them (use the name of a friend at school if you want) and are only operating that computer to help them back up some data from that site in case they lose it. In exchange, they let you use that computer for your own personal use whenever you choose. Or something to that effect, saying that you weren't exchanging ownership of the data, but merely transferring it from one hard drive to another.