memtest86, see if that passes, sounds like RAM or mobo to me. try it with minimal amount of RAM in, then try a different stick in a different slot etc. I'd also check temps.
It's unlikely to be software, but it is possible. Since you think it only happens when you update windows, turn off auto update and then try running prime95 small fft's torture test on all cores, if that passes 30 minutes-an hour try a blend test for at least an hour (this tests ram + cpu). The blend test could freeze/reboo tyour pc which will tend to mean dodgy ram.