Xbox360 Help Please!!!?

So I had previously asked about why I kept having the Open Tray problem and we kinda fixed that problem...We took apart the xbox and moved the laser closer to the disk tray and that made it start working. But the laser is pretty much right up against the disk tray so maybe thats the next problem. Now that we got the games working, there is a ridiculously loud hum coming from the xbox. It only happens when Im playing games. Never on the xbox home screen. What could this problem be?