The installation failed in SAFE_OS phase with an error during INSTALL_RECOVERY_ENVIRONMENT operation OxC1900101-ox20004
So I spent a few hours struggling to install the Windows 10 upgrade on my Windows 8.1 professional computer. My install of Windows 8.1 was clean except for Microsoft Office 365 and Firefox. Each attempt to install the Windows 10 upgrade failed at 25% and 84% copying files. It tried loading from the desktop as well as USB. The resulting error after the failure was always “The installation failed in SAFE_OS phase with an error during INSTALL RECOVERY ENVIRONMENT operation OxC1900101-ox20004“. A bit of research showed others with similar issues but not my EXACT issue. Not having many options I kept my troubleshooting simple. I disconnected my Blu Ray drive and drive bay usb card reader. Upon reboot the computer reached the 25% point and I waited with baited breath. Just as I was about to think I failed the install shot to 30%. 10 minutes later I was at the Windows 10 desktop.