Win10 repair install with a MBR USB stick while C: is GPT (UEFI)

My C: is GPT, running fully in UEFI mode, I believe. This is Intel NUC6i5SYK. I'm trying to do a repair install. So I tried making the Win10 bootable USB with Rufus (and Windows USB Download Tool). Only making it in MBR it boots. If GPT, it doesn't boot.

1) If I repair install while the USB is in MBR mode, is this fine and C: will stay fully GPT and UEFI?

2) Why can't Rufus make the GPT stick boot? (I downloaded also Easy2Boot but I didn't try that yet.)

cereberus said:

Use the media creation tool to create your usb drive -it boots on mbr or uefi pcs.

Hi there
while that is the best suggestion I'm surprised at the boot of your rufus stick you don't see 2 options to boot -- that happens on my HP Envy laptop - 1 will boot OK normally while the other will probably error out with message "no OS found - insert Boot disk" or similar.

Anyway the easiest is the previous suggestion - use MCT.

Cheers
jimbo

Ok, I now used MCT to create the bootable USB. What happened was it created a 32 GB FAT32 partition which is MBR. While my C: is GPT. So apparently it's ok to have an MBR USB stick for a repair installation of Windows 10 which is installed in UEFI mode (as I can see in System Information).

I did not do the repair installation yet.

You do not need a GPT partitioned drive to boot in UEFI mode. All that is required is for the proper UEFI boot files to be present in the partition, and most computers require that partition to be FAT32 formatted to boot from it. You do however require UEFI booting in order to boot from a GPT partitioned drive.

If you do a repair install you don't boot from the USB you just click on "setup.exe" while you are running Windows.

It therefore doesn't matter if your USB is MBR or GPT, whether it boots your system or not or indeed or if you just downloaded the ISO to your desktop and ran it from there.

Repair Install Windows 10 with an In-place Upgrade | Windows 10 Tutorials

You didn't do a bad thing. I learned about MCT and that was a very valuable thing to learn!

I agree, I have to start setup.exe from desktop for the in-place "upgrade" = REPAIR.

I also solved the USB not visible at boot problem. That was because Fast boot was on. It has to be Fast boot OFF or USB devices are not initialized. A bit stupid, the boot menu should say "NOTE: Fast boot on, USB devices not initialized" if fast boot is on.