So what happens is, I was using disk clean up and didn't know what compress file is (and it shows using a lot of disk space) so I checked it and then realize that this was an option to compress files for the C drive. I managed to stop it in midway but some files already compressed.

So is there anyway to use PowerShell or software to find those compressed folder/files and decompress them (or show which folder is compressed)?

  • If you set the drive to uncompressed, the compressed files will be decompressed and the others will be ignored. – AFH Mar 2 '19 at 19:48
  • Add on for reference for above comment: Some file that was compress was access denied (likely system using it) so decompression failed. I'm able to use the answer below and access emergency cmd prompt to resolve it. – zhiyan114 Jun 18 '19 at 10:48
  • If you compress C: from the live system, then certain system files will be in use and cannot be compressed, but I would not expect a lot more files to be locked when you decompress. To compress or decompress all files you need to be running from a different system disc, either by booting a different system, such as a diagnostic disc, or possibly from safe mode, though I have not tried the second of these. I didn't know about Keltari's command, so I am glad to learn of it. – AFH Jun 18 '19 at 12:11
  • It weird the fact that some file was compressed and later (canceled the compression process) cannot be decompressed. – zhiyan114 Jun 19 '19 at 4:14

From an Administrator command prompt type the following:

compact /U /S:"C:\"

This will uncompress all the contents of the C:\ drie

  • Didn't work on command prompt even with double backward slash. It just shows some files are still compressed as well as none of the file was decompressed. – zhiyan114 Mar 2 '19 at 20:44
  • EDIT: I managed to decompress all the files using this, thanks and one more questions: are folders under C:\Windows\servicing\Sessions suppose to be compressed? – zhiyan114 Mar 2 '19 at 21:00

In explorer do a right click>Properties on the C drive and Un-Tick "Compress this drive to save disk space" and hot OK.

Also see this page for powershell commands to find compressed files if my answer does not work.

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  • Thing is that is unticked and some file is compressed and cannot find the one that is compressed. – zhiyan114 Mar 2 '19 at 20:02
  • @zhiyan114 Some files on C: will always remain compressed. There is a whole bunch of system-files that are always compressed and will always remain compressed, regardless of that setting. And when you remove that checkmark it can take a while (minutes to hours!) before Windows has decompressed everything. So it isn't strange that you keep seeing some compressed files. Don't worry about it. It will sort itself after a while. – Tonny Mar 2 '19 at 20:07
  • @zhiyan114 see this page....serverfault.com/questions/452529/… – Moab Mar 2 '19 at 20:08
  • @Moab thanks, it worked so is it possible to automatically uncompress them? Since it shows I have quite a lot of files. Also is it possible to uncompress before system bootup (e.g advanced command prompt for debugging) since some file may be running and cannot be processed? – zhiyan114 Mar 2 '19 at 20:22
  • There may be but have no clue how to, sorry. – Moab Mar 2 '19 at 21:06

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