Windows 10 - can be my UEFI and MBR conflict?

Not an issue with your hardware - only the manner in which you attempted to use it, the firmware, and the software.

Last question i will be very greatful for response.
Also i know that UEFI firmware can emulate BIOS functionality (CSM/Legacy) and work with MBR disks just fine.

So why it happened when i change boot from UEFI USB to SDD?

Somebody said to me:""If you switch boot devices, try to keep them in the same family. If you use NON UEFI CD/HDD/SSD/USB on everything, don't switch any of them to UEFI or strange things may happen (and if you use UEFI don't switch to BIOS (aka Legacy).

I wouldn't worry about it, just try to avoid the trigger (switching your boot order around from USB to HDD). Or at least, if you know it's
going to happen, you know how to fix it! <grin>."



Maybe because i switch then?


My bios settings are on default and my disk was formatted in MBR partition. CSM was ENABLED.

xxx123 said:

Last question i will be very greatful for response.
Also i know that UEFI firmware can emulate BIOS functionality (CSM/Legacy) and work with MBR disks just fine.

So why it happened when i change boot from UEFI USB to SDD?

Somebody said to me:""If you switch boot devices, try to keep them in the same family. If you use NON UEFI CD/HDD/SSD/USB on everything, don't switch any of them to UEFI or strange things may happen (and if you use UEFI don't switch to BIOS (aka Legacy).

I wouldn't worry about it, just try to avoid the trigger (switching your boot order around from USB to HDD). Or at least, if you know it's
going to happen, you know how to fix it! <grin>."



Maybe because i switch then?


My bios settings are on default and my disk was formatted in MBR partition. CSM was ENABLED.

Look at your screenshot in post # 12 - it shows the USB as a UEFI bootable device, the Samsung NOT (no "UEFI" in front of it).

Exactly: because you were configured on BOOT screen for UEFI boot and switch to a first boot device that was NOT suitable for UEFI boot (MBR Samsung disk) and Windows was left on its own after boot failure and found an alternative means to boot. Definition of Insanity: doing the same thing over and over again and expecting the outcome to change. If you made no change in BIOS to switch to Legacy Boot, you would continually have the failure to boot 1st time and Windows finding a way to boot itself (2nd boot).

I would say that the advice you got to make up your mind over sticking entirely with Legacy Boot (use MBR) or else sticking entirely with UEFI (use GPT) was good advice [see my "2)" in my post # 17]. I would opt for sticking with UEFI/GPT going forward and only revert to Legacy Boot in special circumstances that may occur on rare occasions.

xxx123 said:

Yes but why system working fine and booting properly once ,just before i change "UEFI USB KINGSTON" to "P1 SSD SAMSUNG EVO 250 GB". Before i do that system booting properly even if i had primary P1 SSD SAMSUNG EVO 250 GB.

Problem with Automatic Repair started after i change in my UEFI boot priority from :"UEFI USB KINGSTON" to "P1 SSD SAMSUNG EVO 250 GB". Any idea?:] This is my last question and sorry for problem .

That would be hard to answer with certainty. We would have to know:

1) Are you sure it actually booted from the Samsung (as MBR) ? Was the Kingston drive bootable and can you be sure it didn't boot from that?

2) Is it possible you actually had the BIOS configured for Legacy boot at the time and it booted from the Samsung (as MBR)? You said it was switched to BIOS defaults at some time - was it possibly configured for Legacy boot and you reset defaults and had booting UEFI for all the other attempts?

Unless you reproduce that precise behavior and then give all the particulars on settings and devices actually present for boot, it seems like it would be useless to speculate at this point. I understand your burning curiosity at on that one question but, unless you have way more time on your hands than I do or another TenForums member can explain things in a way I'm unable to, I would just move on and enjoy what now sounds like is a properly configured and operating UEFI/GPT system.:)

xxx123 said:

..So i dont know if it was Partition/bios issue ?...

Hard to say - one or the other, both, or neither. I will say the trail has gotten a bit cold on this though.

xxx123 said:

...So if UEFI can emulate BIOS functionality why then it get corrupted to Automatic Repair? ...

Because you have to actively change the options in your BIOS to boot Legacy instead of UEFI - it doesn't switch itself automatically. It doesn't know in advance whether you are expecting it to boot from an MBR or a UEFI partitioned device. Repeated attempt to boot MBR device while BIOS is configured for UEFI boot = frustration.