Sudden decrease of ~5GB in free space in C:

[jglamas]

Hello,
I recently noticed that my drive C: decreased in around 5GB.
I have my HDD partitioned in 2 (100GB for C: and 350GB for D, and I store everything in drive D:.
I have kept my drive C: with around 30.5GB of free space for several months now, but since last week that suddenly dropped to 24.8GB.
I checked with WinDirStat, which shows that C: does have 69.5GB in use. I don't know if this accounts for the part of the drive that I'm not allowed to use though.
I do not recall having installed or downloaded anything that large. I did update my Avast antivirus and downloaded some windows updates I believe. Disk Cleanup did not show anything large, and the Disk Defragmenter says it's 1% fragmented.

The file attached shows WinDirStat's results. My Users folder has my drobox folder using 4.75GB, which is almost half of the current Users size of 10.4GB. Unless it was empty before, I don't think the 5GB decrease came from here.

Am I missing something? I'm not really in need of that space if it's something unavoidable, but I am worried of spyware and viruses. Avast doesn't detect any threat so I can't be sure if it's that.

Any help would be appreciated. If there are better tools, I will try with those too.
Thank you.

 

[richc46]

The space is used by system restore. Delete the restoreoints. Then make a new one in case it is needed. I think that your problem will be solved.
http://www.sevenforums.com/tutorials/336-system-protection-restore-points-delete.html

 

[jglamas]

Richard,
when I updated the antivirus, the system DID create an additional restore point.
This helped me very much, thank you.
I deleted all but the most recent restore point, and decreased the maximum disk space usage for restore points.
I'll mark this thread as solved now.

Regards.

 

[richc46]

That's great news. Glad that you were able to solve the problem.

 

[jglamas]

Richard, thank you for your help the other day. Unfortunately my problem was apparently not completely fixed.

Using the steps above I erased old restore points, which freed up more than enough space.
I also decreased the Disk Space Usage for system protection which was at 50 GB by default.
I decreased the disk space usage to 10 GB first, but after a couple of days I had the same problem and when I checked the space usage had been reset to 50 GB.
I repeated the process but it keeps resetting always to 50 GB. I also tried it from extended command prompt (vssadmin Resize ShadowStorage /For=C: /On=C: /Maxsize=10GB) but it still goes back to default.
It doesn't reset immediately, and I checked right after restarting and it hadn't reset yet, but after a couple of days it goes back to 50 GB.

I don't believe that I'm doing anything out of the ordinary (ms office, web browsing, reading pdfs)
Is this expected behavior? Or am I missing something?
For now I'll just delete old restore points if they start using too much space.