I now know this:
But I did not change any hardware, and system restore did not work.
This makes me believe either the RAM failed, though my BiOS 'should' tell me so, or a corrupted NTFS problem.
Since I forced the shutdown last time, I think it may be the latter. However when I try to Chkdsk it, it says it is write protected, though I should be the admin. And write protected is by default disabled in BiOS