What is this noise?

does it sound like a shaver? if it does its your Hard drive. sudden electricity breakdowns can damage a hard drive. we know that the speed of the disk inside the hard drive is 5400 to7200 rpm and a sudden black-out will cause your disk to put on the breaks and floor it at once instead of like a soft shutdown where it breaks slowly. a sudden stop on the drive wont park the disk pointer away drom the drive surface thus creating scratches on it, too many scratches will create the noise and in the long run it might damage your disk totally.

I suggest a good investment on a UPS (uninterruptible Power supply) so that you can safely shut-off your PC then a power failure occurs

Unusual noises coming from disk drives are a cause for concern. My first step would be to back it up. Next down load HDD Health and let it run. Its free and excellent. It will check out the health of your hard drives. You will find a link to the site below.

If your disks are healthy, I would then look into housekeeping: cleanup and defrag etc. I've had badly fragmented drives that caused the heads to go crazy, which resulted in the drives getting hot and the fans running overtime. That could be it.

Basically there are a few components that "make" noise. You just stricke-out 2. It could be power supply fan or graphic card. Some desktop casings have a few fans.

Try to open up the casing & trace to where the noise come from. It will be easier that way.

Hope it helps!

sweet heart there are two fans one for your pc and other the processor fan i think it is th processor fan, or open it up and then turn it on and see where it is coming from

may be affect your Hard disk some virus.