Once your computer starts making weird sounds, sounds that you have never heard before, the culprit is usually your Hard Drive. Usually loud clicking sounds are the hard drive going bad. In order to determine if the Hard Drive is dying out and reaching its end, you need to run diagnostic software to check the drive.
Please provide more info about your PC so that I can further guide you.
What kind of computer do you have? Manufacturer? Model? What model Hard drive do you currently have? How old is the PC?
Please provide the above info...