Computer makes car idle noise - RealWorld forums

Hi. My computer, ever since I 'revived it from the dead,' has been making a... strange noise.
It sounds like an idling car. It just goes "Drrrrrrrrrrrrr..."
It used to be just every now and then, and it seemed to be on specific occasions - For example, I clicked a button on WinRAR and it made this noise.
It doesn't go away until about 3-5 minutes pass...
Now, it happens ALL THE TIME!!!
This is really annoying. It isn't REALLY loud, but my computer isn't in the family room or anything, there is no background noise to distract me, either...
The noise goes on for 3-10 seconds, stops for like half a second, and repeats.
COMPUTER SPECS:

CPU: Intel(R) Pentium(R) 4 CPU 3.00 GHz (32 Bit)
RAM: 512 MB (Stock)
Graphics card: Intel(R) 82945G Express Chipset Family
OS: Windows XP Service Pack 3
BIOS Version: A06
Make: Dell Optiplex
Model: Optiplex GX620

I have tried to turn the performance mode (I think it was Acoustic noise or something similar) from performance to bypass, ad this seemed to start the issue, but it didn't work.
I tried going to this symptom diagnostic partition that I (THANKFULLY - SCORE DELL) have on my PC, and it turns the fans to high, then low. No difference in the noise, on low I still hear it.
It then tries stopping the hard drive, but the PC still makes noise. I am stumped. What else could make this noise???

It probably is just your fan you hear. They get old and dusty and make noises. Try cleaning it with canned air.
Get used to the noise or play a radio or tv in the background. You may want to replace your fan if it keeps bothering you after a while.

Okay. I can't replace it, though. My parents don't want to spend money on a 8+ year old PC. Also, it isn't the fan. Like I said, I turned fans off for a second, and the noise carried on. However I don't hear it anymore, thanks for your consideration.

Nevermind, it still makes the noise, it's just really quiet. Perhaps it was supposed to make that noise, but not as loud.

My seven years old Acer netbook started to make that drrrrr noise a few years ago, too. But it's the Acer's harddrive.
A very interesting soundscape:
It growls like a lawn mower gone batshit crazy each time I start or restart that computer.
The Acer survived an old Thinkpad, and now I'm here with a second hand Dell laptop. Both were considered to be replacements for the Acer netbook, because I thought twice the Acer wouldn't do it much longer.
Weird computer.

U have better machine now?

Sorry it sounds like it is not just a fan.
Hope you can resolve your problem soon.
My pc is running quietly for the time being but it has been quite noisy in the past so I can sympathize with you.

My school laptop is 100% QUIET. My fan is 100% QUIET. It doesn't make a car idling noise at all. This is a Lenovo EDU Series Windows 8 laptop.

Late response, but I do have a new computer. However I still think my old computer is useful (It is perfect for work like making icons and cursors) and it does not seem to make the noise anymore. If your case scenario is right (Hard drive issue) then I had better worry; I still have files I cant' migrate. However I looked on google once before and found no noises like the one I heard. I'll check again, maybe.