Computer Intermittently Makes Bad Noise

[commodiusvicus]

Occasionally, during the past couple of months, my desktop has made a horrific lawnmower noise upon waking up from hibernation until i shut it off (which i have done very quickly and in a panic each time it's happened). It is quite loud. I believe it also happened once when the computer had been off as opposed to asleep. The intermittent nature of this problem makes it difficult to pinpoint where it's coming from. I keep my system very free of dust.

I can think of only two significant things that have changed since the first time i encountered the problem:
1) I installed a new video card
2) I downloaded Intel's Core Temp monitor. It seemingly nearly killed my system, even though i have an Intel motherboard and processor. The first time i ran the program, it immediately caused my CPU fan to briefly rev up to lightspeed. Before i could even reach for the power switch on my surge protector, the computer had shut itself off. I had to reset the CMOS and do a system restore.

Specs:
Dell E520 running Windows Vista
Intel Pentium D925, 3 GHz
Nvidia 8400GS Video card (not overclocked)
2 gig RAM
All internal system components (besides the video card) are stock

I've been backing up my files every other day but other than a terrifying interlude every once in awhile nothing bad has happened yet. What on Earth is going on?

 

[mrmaia]

It most probably is one of your fans, specially the PSU one. When the fan bearing lifespan is over, its internal components suffer MUCH more friction and thus the sound.

Try listening carefully to your fans and pinpointing the problem one, and take care cause a bad fan can lead to hardware damage.