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I am facing low disk space issue from last few days. I checked with Restore,System Volume Information, $Recycled folders. But there is nothing which is occupying space. I had scanned my system for virus too.

Total size of C: is 18 GB. But when I select all folders inside C: and query for used space, it shows 20+ gb space is used.

I vacate space some how by deleting temp files, program's cache files, disk clean up etc up to (3 gb). And I ensured that no cache/temp files are recreated who can use the space again.

Even after cleaning so much data, I am again facing low disk space issue. Something is eating disk space within 15-20 mins.

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As in Total Size, you mean 18GB of free space right? Because 20G of free space shouldn't fit inside of 18 – cutrightjm Apr 15 '12 at 2:53
If it is eating up disk space in a short time, viewing the resource monitor Disk Tab might reveal something. Viruses will sometimes use the temp location, as a base of repetition. On the other hand system restore finds a hole and fills it, and the recycle bin is self cleaning of older files. Any way you look at it, finding out what it is. – Psycogeek Apr 15 '12 at 2:58
@ekaj, 18GB is capacity of drive and 20+ gb is used space(when i select all files and press alt+enter). looks strange but it is. – noquery Apr 15 '12 at 3:13
possible duplicate of How can I visualize the file system usage on Windows? – Ƭᴇcʜιᴇ007 Apr 15 '12 at 4:40
up vote 9 down vote accepted

Check out Process Monitor utility from Sysinternals Suite and see what files are being written to.

Also try WinDirStat to see graphically what is taking up so much space.

Here is a good post listing many alternative disk space visualizer tools: How can I visualize the file system usage on Windows?

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+1 for suggesting some good tools for analysis. Will update soon if i find solution or cause. – noquery Apr 15 '12 at 3:23
WinDirStat helped me to find out the cause. It is BitDefender Threat Scanner who eaten my HDD space :(. I am about to delete all last updates. – noquery Apr 15 '12 at 3:48
+1 for WinDirStat. Coincidentally, I'm currently running it to find out where my HD space has gone. – lacqui Apr 15 '12 at 3:50

Check out Spacemonger. It's a great easy to use utility with a really cool graphical representation of the space used on your drive. I use it all the time to quickly assess what's going on with my drives.

Could very well be the hibernate file or the page.sys file.

enter image description here

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similar to windirstat, but I like this too. – Rob Apr 18 '12 at 15:17

A common and often unknown problem with Windows 7 is the hibernation mode. If you don't use hibernation, you should disable it, as Windows will keep a file equal or larger to you RAM on your disk at all times called hiberfil.sys. I had a big problem with this on a machine with a 60gb boot SSD but 48gb of RAM.

There are plenty of guides out there on how to disable it. Try this one: How to Disable Hibernate

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In this day and age and with modern O/S'S, (eg Windows 7 as you are using), you really can't be "gigabyte pinching". The truth these O/S's are CPU hungry, memory hungry, and harddisk hungry. The pagefile alone is default 8gb (C:\pagefile.sys) and C:\hiberfil.sys is 6gb.

Don't play with these. Though they can be modified, the performance loss is not worth it.

Get a bigger harddisk.

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