What did you run for RAM & Disk checking? For RAM it should be a few hours run of Memtest86+
and for the disk it should be Seatools
on all tests except Advanced and Long Generic.
I'm seeing solitary bit corruptions taking place in Windows kernel code. No doubt there's a hardware issue, but which hardware can be rather difficult to ascertain. Aside from the aforementioned diagnostic tests, also run Prime95
on Torture Test on Blend settings overnight (make sure your CPU cooler is fit to handle it!). Regardless of the results, you may want to run another test afterwards but on Large FFT settings instead. This can help us discern whether it's an internal CPU issue or something else. Remember that the PSU can also be a potential element of failure.