Hard drive high pitch noise

[nvidiarulesati]

I have a 3 year old custom built pc with a cheap single core AMD and an nVidia 8400gs. After some time i encountered strange problems like BSOD's and random freezing etc. But recently the hard drive started making a high pitched noise and as soon as he noise occurred it would stop spinning and then start back again and then it would all start over.

Im sure its the hard drive since i literally put my head in the case. Just incase it was happening because of something loose i took out my mobo andd reseated everything and started the pc with the necessary components.Still, no luck . So can any1 tell me why the hard drive makes that noise? And by the way it doesnt ever pass POST i tried with onboard video and the 8400gs. HELP PLEASE?

 

[nvidiarulesati]

I just found out that 1 pin in the back of the psu where i connect the plug is burnt i even opened the psu and say that it even melted the plastic :S Im guessing it shorted as this exact same thing happened bfore. Does overclocking have to do with this? its a 500w psu with lots of power to spare cuz the 8400gs uses very little power (less than 50w)