Solved how to get back unaccessible space of 139GB on C drive

I am running Windows 7 Professional 64 on a Lenovo laptop (T410), which I got almost a year ago, used. It had very few programs installed when I got it and up to a few of months ago, I am sure there was less than 100 GB on the C drive. I have not checked the C drive usage frequently to know when exactly this problem started.

I have Avast antivirus installed since I got the laptop and GrimeFighter installed recently on my computer.

I realize last week my C drive is quite full (244 GB in use). I know for sure I cannot have used more 100GB on the C drive. Disk clean up and defrag did not help. SpaceSniffer showed a 139GB of "unaccessible space" which contained no item. I don't know what this space is and what program needs it. How do I get back this piece of space? I searched Google but did not find any useful hints.

Hey, there is a known issue for Avast increasing System Protection max usage to 50%.
It will set it back to 50% if you change it manually too I guess.

You may search the forum or perhaps see a better resolution on Avast forums.

To check if you have this issue:
- Computer r.click->Properties->System Protection->Configure
or
- Control panel->System->System protection->Configure
see the max usage percentage.

Thanks for your help.

- Control panel->System->System protection->Configure
shows
Current Usage as 141.26 GB
and
Max Usage set to 50% (144.21 GB)

Would turning off system protection, changing the max usage, or deleting all restore points resolve this problem? This never happens before. Since I have been using Avast Antivirus fore a few years and did not notice this problem, could this be caused by GrimeFighter?

Thanks,

Please read https://forum.avast.com/index.php?topic=162041.0
Also check https://forum.avast.com/index.php?topic=166697.0

To answer you, no it won't matter if you delete restore points or change the % back to whatever you want it. It will come back after a restart and fill that space again.

You can try:
- go to control panel-> programs and features -> Avast -> change
- remove the component NG.
- change % back to 10% (windows default) or whatever you like it
- restart
- check if % is what you set
- check restore points (seems this NG delete old restore points when run out of space)
- manually crete a restore point if there are none
- open command prompt ->vssadmin list shadowstorage
- see how much space it takes.

Thanks for the detail instructions. I read the Avast forum and did the following:

- changed the system protection space % back to 15% from 50%
- went to control panel-> programs and features -> Avast -> change
but there was no component NG in the change panel to uncheck, so I unchecked Grimefighter since it was the last one I used before I noticed the problem.
- a restore point was created by the change made in Avast.
- laptop was restarted.
- checked the system protection space %, it is still 15%
- cheked Avast to make sure GrimeFighter it was still unchecked
- tried to run GrimeFighter again but it no longer showed up on the Avast user interface so I could not run it like before.
- downloaded GrimeFighter.exe and ran it.
- laptop was restarted after Grimefighter finished.
- checked system protection space, was still 15%
- vssadmin list ShadowStorage command showed maximum shadow storage was 15%
- restarted my laptop manually to make sure that system protection space was still 15% after I did some work
- I checked and unchecked the GrimeFighter box a couple of more times (and restarted laptop) to see if the problem return and it did not
- I also checked restore pointed, I saw 5, 4 from changing of Avast components

So thank you for your suggestions/solutions, I considered the problem solved for now. I appreciated your help.