Hey Den,
From what I've gathered from my professors, as long as you're a student, and you're not trying to make any money off of your projects, you can use other people's music, BUT it has to be less than 20 seconds.
20 seconds is pretty worthless to me, especially if you like music that has an ambient build or has a layered effect like NIN's stuff, because their songs fulfill a certain mood that has to be listened to for longer than 20 seconds in order to feel the effect.
Anyhow, if you're interested in composing your own tracks for your own films so you can be all original, it's not that difficult, and you'll be able to do stuff like Reznor pretty easily. There are a number of music composition software applications available. I've used Apple Soundtrack to do some of my stuff, I’m not entirely pleased with the selection of loops, which can be pretty generic, but there’s quite a bit of freedom given as to how I want to filter it, and structure it, so it kind of levels itself out. Adobe’s Audition is said to be pretty good too.
I guess it all just depends on what you want to do with your films, but I think you're moving in the right direction; even if it's all for Nothing...Ok that was stupid, but I had to...
