I can tell it's coming from the front of the computer...which means it's either a hard drive or a fan. It happens most often when the computer is idling or loading a web page. I'm thinking it's the Hitachi hard drive. It says my MFT usage on the hitachi was 99% so I increased it and it says the drive is healthy now. I am defragmenting my other drive just in case. It says the MFT usage on the other drive is 94% so I will increase that too. I don't think it will help the clicking. Although since I started the defrag on the western digital hard drive the clicking has stopped...but then again I did just mess with the other drive.