Something changed SSD format from GPT to MBR

Slatey · 17 May 2017

Updated from W10 1508 to the anniversary edition early this year - 250gb SSD as main drive, and system clone on a 750gb SSD/HDD hybrid, both GPT format. After a month or so the OS on the SSD crashed, and I could not re-load W10. Was told that the drive was formatted MBR. Switched to the clone, everything was ok for about three weeks, then it crashed. Same problem. Reformatted both back to GPT, loaded W10 1703 onto the SSD, now running with no problems. Still to do the clone.
Does anyone have any idea what could have caused this? I have only found one similar reference on the net, and that involved W7.
I have on two occasions had the UEFI/BIOS corrupted, but being a dual BIOS board, have been able to recover that. No corruption problems in this case though.

cereberus · 17 May 2017

Your clone image must be of an mbr based install. Some bioses will run uefi or legacy bios mode automatically - others you have to specifically select mode.

Slatey · 18 May 2017

Cerebus,
Started thinking about that after I posted, and yes, probably didn't reformat the hybrid to GPT.
However, what could have happened to the SSD? It was in GPT format before the first W10 install, otherwise it could not have loaded. W10 worked fine for a year. Could a mobo bug or virus have changed the SSD format? Kaspersky could not shed any light on this possibility. MOBO BIOS is set to select UEFI or Legacy automatically.

CountMike · 18 May 2017

I don't know what changed it but if it's running you can do this: Convert Windows 10 from Legacy BIOS to UEFI without Data Loss Windows 10 Installation Upgrade Tutorials
I did it just couple of weeks ago when switching from legacy to UEFI mode.

cereberus · 18 May 2017

Slatey said:

Cerebus,
Started thinking about that after I posted, and yes, probably didn't reformat the hybrid to GPT.
However, what could have happened to the SSD? It was in GPT format before the first W10 install, otherwise it could not have loaded. W10 worked fine for a year. Could a mobo bug or virus have changed the SSD format? Kaspersky could not shed any light on this possibility. MOBO BIOS is set to select UEFI or Legacy automatically.

There is no way a mobo bug could change a drive from gpt to mbr. Even if a virus changed your drive to mbr, it is hardly going to do that without losing all data.

I am betting your first install that you backed up was an mbr install. If you are using pro, you could load the Macrium image file you made as a vm using viboot and look at partitions and that will tell you if it backed up an mbr install.

Slatey · 19 May 2017

Cerebus,
As stated, SSD was GPT format [BIOS in UEFI], when W 10 v1508 was first installed, v1607 and anniversary update also went onto that drive, the cloned hybrid drive [v1607] was probably MBR. I lost all data with both crashes. Most was backed up, so I only lost about 3 weeks worth of emails. In both these instances, I was using the computer, everything was fine, then suddenly just a black screen.
You've lost me in the second paragraph after you reached 'Macrium'.

Am using W10 Home Premium x64.

CountMike
v1703 currently running happily on the reformatted GPT SSD, BIOS still UEFI, so probably not much point in using your suggestion at the moment.
Regards,