It was recently posted by OnMSFT that a small percentage of PCs may fail to update to the 15042 Insider Build. When that happens, your computer will hang on a black screen after reboot. I know … I just encountered it.

Fortunately, I was aware of the bug before I proceeded, and knew where to go to get the fix. thanks to this post from Microsoft Answers!

Here’s what you need to do:

• If you computer already is hung, you will need to do a hard reboot (or two) which should force the computer to revert back to the previous version.
• Then log in, open up an administrative level command prompt, and then type (or copy and paste) enter each of these instructions – one at a time – into the command window:

  reg delete HKEY_LOCAL_MACHINE\system\setup\upgrade\nsimigrationroot /f

  netsh int ipv6 set locality state=disabled

  reg delete HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Nsi\{eb004a01-9b1a-11d4-9123-0050047759bc}\28 /f

• After this, close the command prompt window, reboot, and re-scan for updates.

As always, if you are in the insider ring, it pays to stay up-to-date on insider releases and issues.Insider releases are NOT meant to be run on production machines.