i have the 24" alu mid-2007 iMac and it has been working like a charm since. but recently ive noticed that it had been making small popping noises but i dont think its from my speakers as it happens when no music is playing and its nothing super loud and it happens every once in a while. this also happens with my ps3 and ive heard from people that its just the casing and its nothing to really worry about but i dont know. could it just be the casing or something more serious? like i said it happens maybe once every 2 days and sometimes less.