Is this a sign of an impending crash?
Happy hard drives do not scream.
Have you backed up your important files recently ?
Fortunately, I don’t have any important files. 
Unfortunately, I have to start 3 term papers tomorrow. DAMMIT. I don’t know, it could be the fan, so I had better shut the thing down. I don’t want it to overheat.
Fortunately, my university’s tech department fixes these required machines for free.
Yes, it’s probably going to die soon.
Does it scream all the time now, or only during reading/writing?
It’s probably a prelude to failed bearing. Back it up and/or replace it.
Well if you’d stop beating it with a switch it might just stop screaming…
Oh and if you are more specific, some one might be able to come along and help you out…could be that it’s off it’s “spindle” if you knocked it around recently.
I bought a Sony Viao laptop a few months back that did this, and I couldn’t shut the fucking thing off, I ended up having to take out the battery. Come to think about it, I had an IBM Think Pad that did the same thing. Are you using a notebook PC?
If it’s the disk drive screaming, you probably wouldn’t be able to boot. If you can boot, it’s more likely the fan.
Can you open the case? Roll up a sheet of paper, put one end on the disk drive and the other end to your ear. Try the same thing with the fan. This should tell you which one’s in pain.
You may have a CPU fan, a box fan or both. Box fans can easily be had at Radio Shack. CPU fans are sometimes bonded to the heat sink which must be thermally bonded to the CPU. You can do this, but you have to follow the instructions carefully. Other types can be snapped on easily.
The HDs I bought recently, like a year or two, have a cool bios feature called s.m.a.r.t they let you know when your HD is working properly & warns you if necessary. If your HD has it you might turn it on in the bios.
Of course, you’ll also need diagnostic software that is capable of interacting with the s.m.a.r.t. feature.
what software do you use Jeff? I didn’t know there was any because its a BIOS call.
I don’t have any, that’s why I turned mine back off. I don’t recall who said that compatible sofware is needed but it’s in the thread I posted regarding my own computer woes over the summer.
if it makes you feel any better, i just got off with a customer whose modem is making honest-to-god pig noises. it sounds like a hog sawing wood.
i’d consider that somewhat scarier than screaming.
worse would be this trick that i heard nt servers do when one of their fans starts to go out: they start playing “it’s a small world.”
My old boss at a company I worked for during grad school had one of those old orange hard disk platters about 12 in across hanging on his office wall. It has these deep gouges in it going around the platter. The story is that he was sitting in his office at DEC when somebody came in saying the audible alarm was going off on the disk drive. Those drives did not have an audible alarm the screeching noise was the heads grinding against the platter.