Hi - I'm an IT professional with a baffling Windows 10 problem (Pro 1809 10.0.17763.615/semi-annual channel).
Recently over 300 GB of space has mysteriously gone missing on an NTFS system drive, and none of the tools I've found can tell me why. It's unclear exactly when the problem began, because the missing space wasn't noticed until the drive reached capacity
during normal operation. Windows Storage settings reports a whopping 347 GB for "System Files", but I suspect this is a display glitch as the space doesn't seem to actually exist in any files on the file system.
- Searching the entire file system (including hidden folders) using WinDirStat, SpaceSniffer, Cygwin du, and others running with administrative access
- Repeated on-line and off-line chkdsk (no errors)
- vssadmin list commands to audit shadow copies
- dism scans (no problems)
- Unprivileged and Administrative Disk Cleanup (nothing useful)
- Full virus scans with Windows Defender and AVG (installed after the problem began) are clean, and I've noticed no other virus-like activity.
- Drive-level diagnostics: SeaTools and Samsung Magician (all clean)