Tried to return O/S to factory settings & 61% through the process the tablet froze? Waited almost 2 hrs never did a thin? so I powered off & rebooted but it goes to an preparing automatic repair screen then diagnosing your PC, then says  attempting repairs then I get automatic repair couldn't repair your PC.Press shut down or advanced options, which at that point the display won't react? So I have no choice but to power it down & reboot using either up or down volume key after pressing power key, I have tried to set boot options to USB which is not listed, but have it set to secure boot OFF, but can't seem to figure out how to change the UEFI setting and of course the tablet is out of warranty! I have the media USB stick from dell just can't get tablet to boot from it? Any HELP with this Issue would be gratefully appreciated.