noises - I was worried about HD

Just about a week ago, my HD started making intermittent clicking noises. It's sort of like the noise that a laptop HD makes when it parks its heads, only much louder. It only happens three or four times a day, and I definitely can't reproduce it. I've had the computer for almost a year and it's never made any sound like that before.

I've read that sudden noises are usually an indication that the HD is dying, but every single utility scan I run (MS Windows 2000 ) tells me that there's nothing wrong with the drive (I have Seagate HD).

Is it possible that a drive has physical problems but a software utility can't pick it up?