I am trying to help recover a PC running Windows 10 that appears to have had damage to a system file (perhaps a disk error, virus); or maybe this is a registry problem show how. When logging in (to any account) the message appears: rundll32.exe - Bad Image C:\WINDOWS\SYSTEM32\sfc.dll is either not designed to run on Windows or contains an error. Error status 0x000012f. It turns out this error had been present for some time, and is now written into the system image backups . Searching for fixes I have found suggestions to run a system reset, run "sfc /scannow" to fix system files, and run "Dism /RestoreHealth" (with WIM or ESD Windows 10 distributions). None of these solves the problem. I have tried a reinstall from a virtually mounted ISO; this gives an error message (I didn't record the error code). I am guessing that sfc.dll is key to any system repairs short of an install from scratch, and to function all the above require sfc.dll and/or related registry entries (if these cause the .dll error message). Next step I will try a recovery or clean install from a USB ESD. Unless someone can suggest how to specifically repair sfc.dll (apparently the critical hub for system repairs) ?