Unmountable boot volume

[shlars1936]

I have a PC that recently spontaneously upgraded to Windows 10. Today it was booting up. After about 3 minutes of booting, it gives me a blue screen, saying it ran into a problem and needed to restart. For more information, visit windows.com/stopcode ,and my stopcode is Unmountable boot volume. It then restarts, shows a black screen saying "Preparing Automatic Repair", and then gives me a completely black screen, and that's it.

 

[Trouble]

Hello and welcome to the forum.

a black screen saying "Preparing Automatic Repair", and then gives me a completely black screen, and that's it.

How long have you left it on that "black screen"
During that time can you determine if there is any hard disk activity? Is the computer equipped with a hard disk activity light? Can you hear or feel the hard disk spinning?
It is not unusual for that screen to remain in place for hours until it succeeds or fails at the task.
Normally if it fails it will loop a reboot cycle over and over again.

 

[shlars1936]

I left it about an hour, no apparent disk activity. You think if I leave it, it will resolve itself?

 

[Trouble]

You think if I leave it, it will resolve itself?

Who knows.... probably not if there is not evident disk activity, but I remember leaving one overnight and the next morning it was running.

You may want to prepare for the worse case scenario though. As you are receiving

Unmountable boot volume

It's possible that you have a corrupt, failing or otherwise physically damaged hard disk.
AND you'll need a working computer.....

You need to build your own installation media to boot your system. Go here.....
https://www.microsoft.com/en-us/software-download/windows10
Get a copy of the ISO and save it to your computer read the subsection titled Using the tool to create installation media (USB flash drive, DVD, or ISO file) to install Windows 10 on a different PC (click to show more or less information)
You can use the media creation tool to write to either a DVD or a USB ThumbDrive but I generally use
ImgBurn to burn it to a DVD http://imgburn.com/index.php?act=download (simply install it and then right click the ISO and choose Open with and select ImgBurn from the context menu)
OR
Rufus to burn it to a USB ThumbDrive http://rufus.akeo.ie/ (just run the program and configure it according to your system needs)

Use that installation media to boot the system click the Repair Your Computer link on the second page after the Choose a Language and Keyboard layout page.That should get you to the Advanced Troubleshooting options.
Sometimes those options work better when attempted from the installation media.
Startup Repair
System Restore
Startup Settings to see if you can get it to boot in safe mode

Failing all troubleshooting steps you can still use the installation media to choose the "Install now" button to perform a custom clean install of Windows as a last resort.
Hopefully you have backups of all your critical data.