Ok, it shut up just as I typed that title. But for like perhaps a half-hour straight, the thing wouldn't shut up. It kept sounding like it was downloading or installing something. I don't know if it could be called disk thrashing, because I only had like one browser window open. Now it is possible some type of scan was running. I have avast and spybot s&d in my system tray, but neither of those seemed to be the culprit. My defrag isn't even scheduled to run at that time. So I have no idea what it was. It has done this crap before. It drives me nuts. If I was not poor, I would have slammed the thing on the ground and busted it to bits with a sledge hammer. Also, it started making this "scanning" type noise. Like it is scanning a CD. But there is no disk in the drive. So I don't even know if it is coming from the dvd/cd drive. It is annoying, but not nearly as bad as the hard-drive issue. I hope there isn't some malware activity causing this crap.
Maybe this is more of a software issue. I would have preferred to post in the vista forum, and that's what makes more sense to me. But since it is the hard-drive making the noise, I thought people would probably say I should have posted it here.
Thanks for reading. Sorry for the tone right now. I am just mad at this thing.

Athlon 64 X2 4400
1024MB of RAM
250GB HD
Vista Home Premium
Nvidia 6150

I would like to add that now I really do not think it is the CD/DVD drive making the "scanning" noise. It could be, but I doubt it. The "scanning" noise is more like a "hiss" and my cd/dvd drive sounds more like a loud jet engine(which also annoys me, but it has always done it, so I just accept it. I think it is supposed to sound like that). But the "scanning" noise is much more subtle and quieter(but still annoying). And it sounds like a cruel, piercing, malevolent hiss.
I noticed that it tends to do it, whenever I go to a different website in my browser. Once when it started hissing at me, I closed the browser and it almost immediately stopped. I don't know if the hiss/scanning noise is related to my hard-drive issue or not. I have a feeling that it is, but I could be wrong. They may be two separate things, but I'm not sure.

I moved the computer to a different location yesterday, and I was careful. Unfortunately, the computer did move in an undesirable fashion and experienced what I perceived to be a small impact of little consequence. I am reluctant to attribute my problems to that occurrence. I did not think it hit hard enough but I could be wrong. Besides, I think I have experienced both of these noise issues before, but I am really noticing them now. Or perhaps the impact simply exacerbated a preexistent problem.

hmmm....
I should probably get some sleep now. lol, I just hope the thing doesn't start speaking to me! :)

Athlon 64 X2 4400
1024MB of RAM
250GB HD
Vista Home Premium
Nvidia 6150

open the case, disconnect the cd drive. see if noise stops.
make sure no belts/wires are in the cpu fan.

Also, if the above doesn't help, try deleting temp files then defragmenting your hard drive...

A couple of weeks back one of the PCs in this office had a hard drive which was making a clicking noise more or less constantly, it kind of sounded like something may have been catching inside the drive.

That was unexpectedly resolved by a defrag...

Given that you've only noticed it since the move, I think the wires/fan answer is more likely (ie you've disturbed something in the move)

Or is it possible that the PC is more open now so you can hear a noise that was there all along but you never noticed before?

Thanks for the replies everyone. I want to reiterate, that basically we are talking about two different "symptoms" here: the "hissing" noise of uncertain origin, and the noise which is certainly my hard-drive(crunching/grinding noise). I suspect that these two noises may be related, but I am not certain.

mountain,
Very good idea. But, I think I may void the warranty if I open the case. So, I may have to send the computer to the manufacturer. I will need to check the details of my warranty and decide from there.

mr1470,
thank you for the suggestions. I will definitely try those. I defragged my HD last week, so I don't know if that is the issue or not.
I am certain now that it was not due to the move. Because I recall a few days ago, I heard a hissing noise. I suspected it was coming from the computer, but I was not sure. I think I ultimately attributed it to water pipes in the walls. But I now remember that the noise is identical to the hissing noise that the computer is making now, and that it is clearly coming from the computer, and finally that it cannot be the pipes any more, as obviously I am in a different building. But anyway, yes, I do clearly recall hearing the noise before this move. The same for the hard-drive crunching noise. I may be just more sensitive to the noise, due to stress that I am under right now from some personal issues, and the fact that the tower now sits in a wood cabinet in an all wood computer desk, which may somehow be amplifying the noise. Even if the noise is being amplified, it still shouldn't be there in the first place though.
But anyway bro, I will try what you suggested with deleting temp files and defragging again.

By the way, any theories as to why I hear the hissing noise when I change to a new website, and it stops when I close the browser?

Thanks much!

Athlon 64 X2 4400
1024MB of RAM
250GB HD
Vista Home Premium
Nvidia 6150

No one has any ideas about this?

"By the way, any theories as to why I hear the hissing noise when I change to a new website, and it stops when I close the browser?"

Athlon 64 X2 4400
1024MB of RAM
250GB HD
Vista Home Premium
Nvidia 6150

I have a brand-new Maxtor 500GB SATA drive that's driving me nuts with its' never-ending crunch-crunch-crunch noise. It sounds as if an imp is inside the HD chiselling away at it. No idea what the problem is. The 4-year old 160GB Maxtor drive in my server is silent in comparison. No idea what the cause is but, like you, I'd like to find a cure for it.