I had a similar problem with a 'tscht' sound. Ends up it was due to the drive overheating -- the onboard fans were not spinning up enough or until the temp became too high.
I downloaded the program
Speedfan which literally saved my hard drive. I ran the program and cranked all the fans in the laptop to 100% and soon the clicking was gone.
Now fans at 100% all the time both are noisy and drain the battery so the next thing to do is look up the specifications for your CPU in terms of operating temperature range and then program that into Speedfan. Voila! The fans will kick in at the temp you specify to maintain the target range. It is an awesome little program.
I'd also recommend NOT defragmenting or running scandisk over and over since that's just going to cause your hard drives to heat up more and more and die faster.