# Why is my computer's HD always churning? **URL:** \ **Category:** Factual Questions\ **Created:** [January 29, 2004, 7:35pm UTC](https://boards.straightdope.com/t/why-is-my-computers-hd-always-churning/226622 "2004-01-29T19:35:40Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Garnet](https://avatars.discourse-cdn.com/v4/letter/g/9de0a6/32.png) [@Garnet](https://boards.straightdope.com/u/Garnet)\ **Post date:** [January 29, 2004, 7:35pm UTC](https://boards.straightdope.com/t/why-is-my-computers-hd-always-churning/226622/1 "2004-01-29T19:35:40Z")
My computer’s hard drive is often making noises like it is accessing the disk, even in the dead of night when no one has used it for hours, and the only screen saver is “blank screen”. It is not continuous, but fairly often. I’ve already checked the computer with both Ad-aware and Spybot updated with the latest reference files, as well as Symantec Antivirus, and no inappropriate processes seem to be running. There is no untoward network activity either, as I checked it in the “Performance” tool. (I am running Windows 2000 here) Does anyone know what could be causing this? The noises don’t sound like “broken HD” noises… could it be a hardware problem anyway though? ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [January 29, 2004, 7:46pm UTC](https://boards.straightdope.com/t/why-is-my-computers-hd-always-churning/226622/2 "2004-01-29T19:46:17Z")
Windows seem will do some automated functions when the computer is unused for a long period of time. Maybe defrag the hard disk or something similar. It’s absolutely normal. No need to worry 🙂 ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [January 29, 2004, 7:49pm UTC](https://boards.straightdope.com/t/why-is-my-computers-hd-always-churning/226622/3 "2004-01-29T19:49:13Z")
Even an “idle” PC is busy as all get out behind the scenes. You’ve probably got all sorts of background processes running (check CTRL-ALT-DEL to see what things you’ve got). These processes may occasionally request memory which is currently unavailable, so Windows uses its virtual memory paging file to “fill in” for RAM by swapping with areas of memory that aren’t currently being used, the swapping this data back when the process that owns it needs it again. This is the most likely cause for your occassional HD acesses. ---
**Author:** ![Garnet](https://avatars.discourse-cdn.com/v4/letter/g/9de0a6/32.png) [@Garnet](https://boards.straightdope.com/u/Garnet)\ **Post date:** [January 29, 2004, 8:26pm UTC](https://boards.straightdope.com/t/why-is-my-computers-hd-always-churning/226622/4 "2004-01-29T20:26:53Z")
It’s not going out to the swap file… I have 768MB of physical RAM and the system only uses about 190 of that. The performance meter for the swapfile finds the max. usage of the swap file to be 1.4%, and it doesn’t change when the HD is doing its thing. I don’t have the Indexing Service enabled, so that’s not it either. CPU usage doesn’t seem to climb appreciably when the HD is going… there are random +/- 2% fluctuations in CPU usage (maxing out at about 4%) when everything else is idle. Well, I guess I won’t worry about it if it sounds OK to you guys… thanks for the advice! ---
**Author:** ![Finagle](https://avatars.discourse-cdn.com/v4/letter/f/b19c9b/32.png) [@Finagle](https://boards.straightdope.com/u/Finagle)\ **Post date:** [January 29, 2004, 8:27pm UTC](https://boards.straightdope.com/t/why-is-my-computers-hd-always-churning/226622/5 "2004-01-29T20:27:20Z")
Probably it’s thermal calibration. Modern hard drives are sufficiently high precision that even minor changes in temperature can cause the platters to expand, resulting in data not being where the drive expects it to be. So the drive runs a calibration every once in a while to adjust for temperature changes. Cite: [http://www.byte.com/art/9412/sec11/art11.htm](http://www.byte.com/art/9412/sec11/art11.htm) ---
**Author:** ![P.Nym](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@P.Nym](https://boards.straightdope.com/u/P.Nym)\ **Post date:** [January 29, 2004, 8:41pm UTC](https://boards.straightdope.com/t/why-is-my-computers-hd-always-churning/226622/6 "2004-01-29T20:41:48Z")
XP has a background defrag routine that’s supposed to optimize file placement for quick booting. I think this is common to W2k. It’s said to be a common cause of disk thrashing on XP boxes. The only way to turn it off is through Regedit. Look for hkey\_local\_machine:software:microsoft:dfrg:BootOptimizeFunction. Set the “Enable” key to N. (I’m assuming you know all about regedit, and the bad, bad things that it can do if used indiscriminately.) ---
**Author:** ![Charlie\_Tan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/charlie_tan/32/12582_2.png) [@Charlie\_Tan](https://boards.straightdope.com/u/Charlie_Tan)\ **Post date:** [January 29, 2004, 10:39pm UTC](https://boards.straightdope.com/t/why-is-my-computers-hd-always-churning/226622/7 "2004-01-29T22:39:05Z")
It’s much easier (if it’s XP, which is notorious for this): [My hard drive won’t stop running](http://www.computing.net/windowsxp/wwwboard/forum/21240.html). ---
**Author:** ![DarrenS](https://avatars.discourse-cdn.com/v4/letter/d/977dab/32.png) [@DarrenS](https://boards.straightdope.com/u/DarrenS)\ **Post date:** [January 30, 2004, 3:43am UTC](https://boards.straightdope.com/t/why-is-my-computers-hd-always-churning/226622/8 "2004-01-30T03:43:56Z")
If you’re really really curious to find out what it is, download Filemon from [www.sysinternals.com](http://www.sysinternals.com) - it will show you exactly what the hard drive activity is - which program is accessing the hard drive and what it’s trying to read or write.