There are many possibilities when HD starts making noise. Some noises are momentary and some are continuous.
You will also get the possible factors which are responsible for such Noises.
*askbobrankin.com/hard-drive.jpg
These continuous Noises indicates possible HD Failure in future for Sure. If you are getting strange Noises, then test these Noises right here:
*www.ecodatarecovery.com/sounds.html
You will also get the possible factors which are responsible for such Noises.