Downgrading Windows 10 to Windows 8.1 "Something Happened" PROBLEM PLEASE HELP

[Besiktepeo]

I originally started to Windows 8.1 Pro and updated to Windows 10 and it gave me HUGE problems now today i decided to try going back but i was running the Windows 8.1 Setup and i plugged in my product key and it said it was succesfull but then it gave me this error for some reason and it says Something Happened Setup has failed to determine supported install choices have tried countless times to figure something out PLEASE HELP ME!

 

[HEXiT]

remove the pc from the net. start the install again.
when asked for a product key just skip it if you can, or enter yours if you cant. then continue...
if it finishes then connect to the net and let windows try and activate. if it fails, its a problem with your key and you will likely have to buy a new 1.
(your win 8 key became invalid 1 month after upgrading to windows 10, from 8/8.1)


if it fails to finish the install properly, then the install media is likely corrupt.

 

[InvalidError]

If you used Windows 10 for more than a month, it is likely exactly as Hex said: your Windows 10 trial expired and now your original Windows 7/8/8.1 activation key is locked to the Windows 10 upgrade.

 

[W Fallon]

Your 8.1 (windows.old files) are gradually removed, and, I believe, completely removed by 28 days.

You'll have to stay with 10 or reinstall 8.1.

Bill