I either hear my fan spinning now or my hard drive. It is a high pitched sound which almost sounds like metal on metal. It isn't really loud, but it does have me a bit worried. Is there a way to tell if it is fan or HD...? I am sure the answer has me opening the Tivo, which scares me a bit. The Tivo is about 5 years old now. Is it typical for the fan to go first or the hard drive?