Hi guys. I bought one of the new-gen iMacs last month--my first Mac! Anyway, here's what's up: My computer will often start making a low-droning noise, and it sounds like a fan. I have iStat, and usually during this time it will say that my Optical Drive and CPU Fan are both running at around 4000rpm. This happens when there is very little CPU usage too. It's happening right now, and I only have firefox running. Is this normal? If not, what should I do? Thanks!!