Make sure it’s not just a blue screen error you are receiving:
-windows will restart automatically if a bluescreen appears
to see if it is a BSOD (blue screen of death) you need to disable automatic restart on system failure
press F8 while your computer restarts and select:
-disable automatic restart on system failure
(this is on the same screen you choose to go into safe mode).
if it is a bluescreen then the stop error code could help us determine what the issue is.
and just to clarify
check disk /r: means repair, and /f means “fix”.
if it’s a boot partition error you might want to try using the “FIXMBR” command while in the recovery console.
one good tool to have is the Ultimate boot Cd, it can do the check disks and also Fix Boot partitions, and even reset admin passwords, check it out.
this should get you going.