Windows Stops Working

[Montego]

My desktop computer build with Windows 8.1 for an OS has been running without flaw for several months, but lately (within the last month or so) I started getting a Windows pop-up saying that "Windows has stopped working and needs to close the program". This happens regardless as to what program I am running (except for my Firefox Browser).
I have been using the same [updated yearly] Norton 'Internet Security' program I have used for several years, have completely cleaned my system using Norton 'Utilities', and have kept everything updated with the latest applicable software.
My question for the community is whether this Windows pop-up is being used as an incentive to upgrade to Windows 10? Perhaps a type of 'NAG-ware'?
Montego

 

[USAFRet]

No, it's not because of anything to do with Windows 10.

Have you looked in the error logs to see what may be happening?