Hi everybody!
I've got a question concerning my hard drive and it's sounds. From time to time the harddisk in my computer makes this weird humming sound. I don't really know how to describe it (no, sorry, I can't record it). It doesn't sound abnormal to me, it's more like a soft seek noise. During that noise, the HDD LED does NOT show any hard disk drive activity. I'm sure, it's not a fan which makes this sound, because I opened my computer's case to listen clearly and it definitely came from the HDD.
It all started in August or September 2008, at least this is when I first heard the sound. I was very, very, very worried back then, because I thought something was wrong.
I contacted Western Digital's support team, but they didn't know either and told me it's probably fine if there's no loss of performance.
About one year later I found this video on Youtube: https://www.youtube.com/watch?v=jbqPBcMVARE and was stunned: the sound during 1:07 and 1:17 is almost exactly the sound my hard disk drive makes from time to time.
At first, the sound would come as soon as my PC finished booting and loading all the programs and during surfing the web. It would NOT stop when I opened a link in Firefox or pressed the refresh button to reload a certain site on the internet. One day the sound was gone and I didn't hear it again for a long time until 2013 when it suddenly decided to come back and occured whenever I listened to music using Windows Media Player for about an hour. I have no idea what it is. Nowadays it usually comes during idle and stays for about 15 to 30 seconds. The sound stops when I do something on my PC like loading something, scanning or starting a certain program (like HD Tune). I also think it's normal since it first came up about 6 years ago and to be honest ... if it was NOT normal, my hard drive disk would have died years ago, wouldn't it?

Further information:
- the HDD is a WD2500JS from the Western Digital Caviar Blue Series (February 2007)
- OS is Windows XP Media Center Edition
- disk indexing is already disabled
- WD support doesn't know anything about that sound
- there's NO loss of performance when the sound occurs
- I've tried different antivirus software (Kaspersky and Avira Internet Security), so I doubt some kind of Idle Scan is responsible for the sound
- I do not use Spybot or similar scanning programs which could be held responsible
- I ran Filemon when the sound occured, but was unable to detect the source of the sound since all the processes running are the same ones running when everything is silent
- Windows Task Manager didn't help me either ... 0% CPU usage during the sound
- there's no defragmentation program running in the background, at least not that I know of
- I ran CHKDSK and several other tests for hours which all came back fine

Does anybody know what that sound could be or what it means and why it's there? I would really appreciate that. I've been searching for the reason of it for years now.

PS: Sorry, for any grammatical errors I may have made. English is not my first language

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