Two NUC5PPYH with startup problem

Hi. I bought a NUC5PPHY from Ebay installed with Windows 10. I set a password on it. Then one day I could not enter the password, neither effect any reset, etc. The seller replaced with another NUC5PPHY, who set to "Admin" with no password. Guess what?, afer using it yesterday, today it went into diagnostic mode on startup, but Windows cannot fix it. And I cannot do any form of reset and I cannot rollback any feature or quality update. Any ideas? What would you do, get a replacement (again) from the seller, or get a refund? Or me install Windows 10 (if I can still do that). As an aside: Can Windows 10 make a backup of the OS only? I don't have Windows version number. Maybe the seller can give me it. Thanks. Rich

Hi. Chkdsk reports a disk problem. So, I might be able to fix the disk and the problem. However, when I use chkdsk /f I get the message "Cannot lock current drive. Windows cannot run disk checking on this volume because it is write protected". However when I look at the volume attributes with DISKPART, it not set read only. And when I use Regedit any changes to the registry, never seem to stick.

I'll do the check. I know what caused the startup failure: I pulled the power cord and that has lead (according to chkdsk), errors on the SSD.