Guessing HDD's too.Does it only do it at start-up or does it do randomly also?Try accessing a file on each hard drive and see if the sound gets reproduced through that.I've had a hard drive fail on me and they make a loud clicking noise and would keep going on like that.Check all your hard drives health and do any error checking on them using a program like HDTune.
I just now realized you said it happens when you start the PC.
For some reason I though it happened when you are already in Windows.
Anyways, my old 250's have had a single loud click to them when starting and stopping for at least the last year and they have been working fine. I am not familiar enough with modern drives to know if that means death soon however.
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