What follows will, in some ways, be eerily similar to what's being described by member Lefty Widdagun in the thread entitled, login screen not presented after installing latest Windows updates.
I don't like hijacking the threads of others and I cannot absolutely know that it was a Windows Update that triggered this situation, though from the client's description I believe it was.
Without any ministrations from me the machine will boot past the Dell Splash Screen, get to the first Windows 10 Splash Screen, then go on to the second with the "black screen with spinning dots", then those dots disappear and you're stuck. The machine is still up and running but never goes any further in the boot process.
Things I've tried so far:
- Booting from an external USB drive with Win10 installation media and running:
- chkdsk - no errors found on the C: drive
- Startup Repair - can't repair
- Rolling back to previous build - can't
- Restoring from a restore point - none available
2. Ran full Dell Diagnostics and everything comes back clean.
3. Tried reinstalling Windows 10 as though it were an upgrade so that all files will be kept. It allows me to make that choice then gives me a dialog saying that I need to restart the computer using regular Windows then insert the installation media to continue. Since regular Windows 10 won't boot this is a catch 22. The best I was able to do was to get to the first Win10 splash screen having plugged in the installation media moments before it popped up and having it say "Please Wait" at the bottom, but no progress from there. No indication of activity on the USB drive and things just sat.
4. Even tried changing boot mode from Legacy to UEFI, which didn't work at all. Once back to Legacy with safe mode turned off I was able to tweak boot order such that USB was first and then do all of what is listed above. I did the UEFI/BIOS tweaks first, but since they didn't work I decided not to list this first. I believe the original boot mode was Legacy with Safe Mode On.
So, what now? The user has some data on the drive that I could easily copy elsewhere and reinstall Windows 10 from scratch, but I wanted to check here to see if anyone has experienced something like this, done what I've done, yet ultimately found a way to make Windows 10 boot again without a "from scratch" installation.