It finally happened to me. I had the latest build November 14, 2017—KB4048955 (OS Build 16299.64) Windows Update installed this: November 30, 2017—KB4051963 (OS Build 16299.98) the install reboot was successful, but the next reboot, well, first time for 'screen of death' in Win 10 for me. from a command prompt, I used 'diskpart' and 'list volume' and discovered my C drive was now my F drive so cannot boot into windows. Even looking in BIOS only Windows Boot loader showed, none of my other hard drives. Nothing I could figure out to do was helping until I used a USB drive I created a Win 10 install on (using MS tool). This allowed the OS to repair it, by rolling the OS back. Now I can boot into windows, but I noticed some small changes, like some files I had deleted were back. All drives show in UEFI bios as well now. Of course the update wants to be installed so I used the option to delay updates for 30 days. Some digging found a post that said if I disconnect all other drives than C, then update, then reconnect other drives should work. Will try later as I must have aged a year during this.