The computer is Asus UX31a (Windows 10) with an non-upgradable 128 GB ssd (115 GB usable) partitioned into 75 GB C and 40 GB D drives.
I need full access to the C drive and have removed everything I can to free up space and now want to identify why there's missing disk space. I want to recover, free up, the unknown, 15 or more missing GBs of disk space.
File Explorer reports C drive has 66 GB usage. But, opening the C drive and selecting everything's Properties shows only 45 GBs of files, not 66. WinDirStat reports 15 GB of 'unknown'. File Explorer, Disk Management, and GParted agree 66 GB is used, but I can only identify 45 GB of files on C drive not 66. What explains the 15 GB WinDirStat 'unknown', and the difference between the 66 GB and 45 GB? There should be about 30 (75-45=30) GBs free space, not only 9.
There must be some process that's locking up that 15 to 21 missing GBs. I ran cmd.exe, C:\>Vssadmin List Shadows and it says, "No items found that satisfy the query." I guess that means there are no shadow copies on the C drive. I scan for malware and find nothing, even with offline scans. Is Windows or some evil actor using the subject disk space for an unknown purpose? Perhaps trim is not working correctly but how can I tell?