Well, as far as I know, the only moving parts in a computer are the hard drive, the fans and the CD/DVD drives. What I would do is to check how much dust is on the fans, as this could potentially cause noise during the startup testing done by the computer. If there is a lot of dust and you know how to, you might try taking the fan off of the computer and blowing the dust out of it. I would also try starting up without anything in the CD drives. If neither of these works, then I would have to agree with CloneAggie about calling a professional.