Applicability: You have been running Windows 7 and have newly migrated to Window 10 on one or more PCs; you still have variously formatted disk drives, some under Windows 7 and some under Windows 10.
DANGER LEVEL: HIGH — Possible Loss of Entire Windows Installation
Microsoft has quietly changed the underlying formatting of NTFS between Windows 7 and Windows 10 generations. While both OSes have the same CHKDSK command with the same options, running it under Windows 7 on a Windows 10 volume will product 1000s of errors and may cause your entire Windows 10 volume to become unreadable under Windows 10. One must particularly be careful to watch for trying to read a 64bit volume under a 32bit Windows 7 or Windows 10 machine. We booted into Windows 7 and ran CHKDSK on a Windows 10 drive, and the following errors scrolled for eons:
Deleting extended attribute set due to the presence of reparse point in file xxxx
We then followed up with attempting to read the disk on a 32bit version of Windows 10 and it told us the volume had to be formatted! Disk manager saw the disk, but could not read the partition at all.
Finally we took the volume over to a 64bit Windows 10 machine and it saw the volume again. Fortunately, I had an image of the original volume, restored it to the drive, and then used 64bit Windows 10 CHKDSK to repair the USB-connected drive volume. Only the real disk problems, an orphaned file or two, were reported and volume was repaired back to normal.
In researching this problem, the common advise found in various Microsoft and other technical forums was to turn Fast Boot off using the powercfg /hibernation off command. While this advise is good, it does not entirely fix the problem because Windows 10 Updates may turn Fast Boot back on. Further, this drive was extracted from a dead laptop and powercfg does not turn off hibernation for an external Windows installation.
Bottom Line: Windows 7 CHKDSK is definitely not 100% compatible with Windows 10 CHKDSK and should never be run to repair Windows 10 volumes.
