That would be you hard drive, the red LED is indicating that it is searching. A clicking noise usually means that your hdd is going out, you might want to back up all of you important file to a removable media like CDs, DVDs, or a flash driv
Most hdd manufacturers have a diagnostic tool that you can download from their web site and run. You will need to open the case and see what the manufacturer is.
After you have downloaded the diagnostic tool and made a CD you may need to change the boot order so the the CD-ROM is the first device seen. If you need help to do this, these
instructions are pretty clear and easy to use.