Weird noise from laptop

[Zirts]

Hi,

So recently I have this weird noise coming from my laptop and I'm not sure if it's coming from fan or HDD.. But the noise is like really really low, like a little fly would be flying around me but even a bit lower than that. But it's a really irritating noise and I want to get rid of it.
Sometimes if I do a restart the noise will go off but after a suspend the noise will come back. What might cause it and what is it?

Oh and it's not my monitor, I can hear the monitor too when I move things like mouse or w/e, it makes a very subtle sound but the sound I'm talking about is just a tad a bit more louder.

[Zirts]

Okay it's coming from my HDD it seems. Whenever the blue HDD activity LED is lighted the sound is even a bit louder. But even when it shows that there is no activity going on, the sound is still coming out of it. It sound like someone scratching the blackboard with his nails but in a really low pitch.

[DeanoCYM]

Does it sound like this?

http://www.youtube.com/watch?v=-xJaE2KARrc

If so, back up before you turn your laptop off.

[Zirts]

No thats really loud noise and it's more like machine scratching. Mine is like a little biiiiiiiiiiip .