Hi there! When I first got my iMac (few months ago) it was so quiet I could barely hear it. Now though, i can hear the fan inside (think its a fan) quite loud. If im watching something, i still hear the fans humming over the audio sound. Is this normal? And is there a way to make it stop? It is placed right up to the wall, as near as it goes.. Is this a problem? Any help is appreciated !!