Hi everybody, after three years of running silent, the fans of my iMac (24" AL, Late 2007) recently started to get louder. And louder. And... I already tried everything there can be done without opening the case - I think they just have worn down. After some searching I found a few instructions for exchanging this Macs harddrive (e.g.: http://forums.macrumors.com/showthread.php?t=350120&highlight=iMac+hard+drive+replace) but none for dealing with the fans. Is there anybody out here who opened his iMac and got a glimpse at the fans? Are the screws accessible from the top or would it be more complicated to replace them than it is with a harddrive?