My Luxo did this once. It just flat out refused to boot. I could hear the fan come on though. I freaked (of course). I went through all the started troubleshooting steps, and a SMC followed by a PRAM reset fixed everything and have not have any hiccups since then. It could be anything. Just keep an eye on it. Interesting, mine is a 2003 1GHz model, like the one your friend gave you.