Just wondering, I've got an iMac - and the fans just went mad for a bit... it's always quiet and never makes a sound, just before it sounded like it was gonna take off...
My MB fans go crazy sometimes if I start doing a lot of things at once, and then they stay on forever. I normally put it to sleep and then the fans turn off and then I turn it back on again.
if you are doing some processor intensive things the fans will become noticable because it is trying to cool the computer down to operating temperature.
The Stig if your MB does it again just let them run there course. Its the computer cooling itself off so it doesnt over heat.