HDD's suddenly noisy?

[DoubleCheese]

Put together a PC this week with two 250GB SATAII 16MB WD Caviar drives and it was lovely and quiet. Booted up this morning and the drives are producing a very loud high pitched sound, similar to a high speed motor vibrating against something.

Any ideas what it could be and what to do about it?

 

[Will_3rd]

Could be your case transmitting the vibrations from your HDDs

 

[DoubleCheese]

Ah, I had three drives in there and luckily it wasn't either of the two new WD Caviars but an older IDE one that I was planning on using as a backup drive. I've taken it out now and its back to silent normality again.