You live in the same house as a guy like this and you don't have your computer password protected? Jeebus. I'm planning to move in with two of my best mates next year for uni, and even I'm planning to keep my computer locked down as much as possible. I trust them and all, but
A - neither of them knows too much about computers, so there's a chance they could screw something up unintentionally, and
B - If it's locked down tight enough, whenver I need to use it, I know it'll be available. Think about it this way - if you'd come in to do some assignment of your own, either you or they (depending on how generous you were feeling) would have been screwed. By keeping them out,, you'd be forcing them to get more organized and ask to do things, therefore leading them both in the direction of becoming fully functioning members of modern society. You'd be doing them a favour.
