Can’t say. Maybe the week before, right after an update, the computer developed a bad case of KSOD (blacK Screen Of Death). I’ve tried all the possible solutions I could find on the internet without being able to fix things.
One known cause are certain Microsoft updates — but how do I remove those (if I have them) when you can’t boot the computer up?
With Windows 7, if it won’t fire up Explorer, the safe mode is not an option.
Repair mode (from the installation medium) thinks the computer booted OK, since it did. (Just that Explorer never started.) Options like sfc, chkdsk, regedit are available from the repair mode but haven’t helped me so far.
And, somewhere along the way the restore points got whacked.