se if there is any cd/dvd in the optical drive if yes then remove it if the sound is coming just when u switch on the pc & disappears when windows is loaded then it is ok
No Mithun there wasn't any cd/dvd in the drive.
Its seems like one of the fan inside your system is having problem. Open the cabby and check if some wire(s) is touching the fan blade.
Remove the cabby cover and start the system, check which fan is making the noise.
@ajayritik: I hope u have cleaned your system.use speed fan to check the fan speed & temp
With my cousin's help I was able to check where the problem was. I opened the cabinet yesterday and found one tiny piece inside the cabinet. I switched the PC on and tried to check from where the problem was coming. It looked like the problem was with the FAN in SMPS. My cousin suggested me to have the SMPS disconnected from motherboard and check and I found that it was indeed the SMPS Fan.
I hope will be able to fix it.
Thanks all for your suggestions.