No boot device detected

[MrMega]

Hello guys, here's my problem:

I started my PC today and I couldn't open any programs. I suspected that it's a problem with my Storage, so I restarted the PC. But when it booted, I was greeted with the "No boot device detected" message. 

The Bios acknowledges that the drive exists, but it doesn't recognize it as a Boot option.

The Motherboard is an ASRock B550 Steel legend and the Drive is a Samsung 970 Evo Plus nvme SSD.

Thanks in advance

[FilipposTechGR]

make sure, 
BIOS is set to UEFI only CSM disabled.
Boot order shows Windows Boot Manager for the NVMe, not just the raw drive.
Drive is in the primary M.2 slot wired to the CPU, not the chipset-only slot.
If it still doesn’t appear, the EFI partition/boot files may be corrupted. Boot from a Windows install USB, go to Repair → Troubleshoot → Startup Repair or run bootrec /fixboot etc. in CMD. That normally rebuilds the boot entry.
Also worth checking you’re on the latest BIOS for the Steel Legend, early B550 firmware had NVMe boot quirks. With all that, the 970 Evo should boot again.

[MrMega]

I have tried to repair it with the windows USB Stick and when I typed in bootrec /fixboot, it said access denied.

As I already said, I realized that there was a problem because my programs didn't launch and Windows stopped being responsive, so I don't think that the boot files are the problem.

[MrMega]

Ok, so I have now put the drive into another computer. I think I'm going to copy my data onto another drive and reinstall Windows, but I can't access some of my files because I don't have the administrator rights from my other PC, is there something I can do to bypass that?