I got a Non-System Disk or Disk Error when I booted up my 2 year old Compaq notebook. After restarting about 50 times over the span of half an hour, Windows eventually started successfully.

Fix MBR2GPT disk layout validation failed, cannot find OS partition, non system disk, cannot install new boot files, EFI system partition errors in Windows 11/10.

When starting your computer system, a 'disk boot failure - insert system disk' error can occur for several reasons, including either hardware or software changes. It is possible to fix the disk boot ...

Yes, that's right: My C: drive is getting errors that are usually reserved for people who've accidentally left a disk in the A: drive! I was messing around with COMMAND.COM, AUTOEXEC.BAT, IO.SYS ...