buzzing, rattling, humming noise with MacBook Pro

I've had my Macbook Pro for around 2 years. About a year ago, it started making a rattling/buzzing noise when I started it up and the noise would vary in strength or stop completely if I tilted the screen back and forth for a while and stopped it in just the right place. The people at the apple store usually act like I'm just hearing things, but then about a month ago one of the guys said it could be a fan problem. So I sent if off for 2 weeks and they claimed to fix it, but when I booted up it started buzzing again new fan and all. They can never seem to hear the noise in our loud apple store, but I'm worried because a friend recently had a macbook making buzzing noises and then her hard drive just stopped working. Could it be my hard drive? If it is, how can I convey that to the guys at the genius bar and could screen tilting impact it? If anyone has a similar problem or knows an answer I would appreciate it so much. There are a lot of buzzing and rattling MBP questions in the forum that I've already read about, but most of the time people are just suggesting it is their fans, and I just got a brand new one. Thanks!