Why I have two computers... (Windows 10 just died)

I did these first two blog entries today on my other computer, in Windows 10 Technical Preview. It seemed to be working fine. But right after I finished that,
I was checking news stories on the Start screen, when something went wrong, and I couldn't get off that screen. 

My only option was to do power switch reboot, and then I got a notice saying that it had run into a problem and needed to restart. That's what I was already trying to do at the time. Then it said "Preparing Automatic Repair", and then "Diagnosing your PC", none of which helped with my unknown problem. The one option that did help was "Use another installed operating system". 

I switched to Windows 8.1, made that the choice for default start-up, and then began a Boot Scan with Avast Internet Security. This scans the drive during a reboot, while the memory is unloaded, and it has access to normally hidden files in the system. It's a slow process though, and I'm still waiting for it to finish.

Meanwhile, Windows 10 and that PC it's on is unavailable. And I'm glad I have more than one PC at times like this. If anyone knows why Windows 10 suddenly went nuts, please leave me a comment. Until now, it has been running great.
I'm wondering "what happened?" 

Continuing on the Windows 10 PC....

While writing this, the faulty PC rebooted, and I got back into Windows 10, and finished running Norton Power Eraser....

NPE found a problem in the Registry's System Settings (bad) and repaired it.

Windows 10 Technical Preview is now up and running normally again, thanks to Norton Power Eraser.

You can download it from here.