I have a Windows 8.1 installation running perfectly well on the above set-up. According to msinfo32.exe and the Windows Disk Management cpl, my SSD is using UEFI to boot - which is clearly the case as NVMe requires UEFI to work.
When I attempt to run a Windows 10 upgrade it fails at the first reboot stage with an error 0xc00000bb error ("A required device isn't connected or can't be accessed")
I am using Bios F8. No combination of settings in the Bios ("Other OS", "Windows 8", etc., CSM enabled and disabled, UEFI or Legacy boot options) allows the Intel 750 SSD to appear as a UEFI device, and I am convinced this is why Windows 10 won't see the drive during installation. The only thing that shows in the Boot Order options is "Windows Boot Manager - [serial number of SSD]". If I have a UEFI USB key plugged in, that shows as "UEFI: Kingston etc...", so why does the Bios not recognise an NVMe UEFI SSD as such? Has anyone managed to install Windows 10 on such a setup?
I can see the problem with the C: Boot being a UEFI. This apparently is what MS wants, for you can enter UEFI via Windows. It is a solo gig, with the option of installing another OS (Unix Linux Mac) as a dual boot, being restrained.
The other option is to use a "layer" of UEFI, and have your C: Boot a Master Boot Record and its System Reserve.
This task is only suitable for C: Boot drives that are less than 2.1TB, as this is the upper limit for Master Boot Record drives, otherwise BIOS will have trouble reading it.
BTW, if your boot drive is over this amount, it is probably best to "initialise" the HDD or SSD as GUID - before - you install Windows 8 upon it. But you suffer the MS thing. There may be some way around it, lets just wait.
I have found a way to enter the BIOS without too much trouble.
Leave your C:Boot as a Master Boot Record, (with its System Reserve Partition) the way that it normally is.
BTW, Dell, HP, Acer all use the "Pure" UFEI at C: when they build their systems, just to please Microsoft. They initialise their drives first, before installing Windows 7,8. Selecting Windows 8 in BIOS is really unhelpful, as Windows boots faster itself.
The rest of us use the "Layer" of UFEI that sits on top of the basic BIOS
Without drives attached, do an update to your BIOS. Try to use the USB 2.0 thumbdrive method within the BIOS, as this is more user friendly. Reboot>Check BIOS version>Load Optimised Defaults. Reboot. It will cycle to no boot record. Sadly you will have to press your "power" button to shut down.
Without drive being present, enter BIOS and change a couple of things. Make sure "Full Screen Logo" is de-activated and that "Fast Boot" is turned off. This allows the AMI BIOS splash screen to appear for 3 seconds. Save and exit. It will cycle to no boot record. Sadly you will have to press your "power" button to shut down again.
Now attach your C:Boot MBR drive and try out hot and cold starts and re-starts. With (Del) to BIOS.
Attach all your drives, and boot to Windows. They will show up in Control Panel>Computer Management>Disk Management.
Here you will see all your drives. You may notice your non-C: drives may be missing 100 to 350 MB of space. This is because there may be hidden partitions (or MBR) on these drives.
Download "MiniTool Partition Wizard Free". You may see the "hidden, but now revealed" partitions on your non-C: drives that you could not see in Windows. Delete these small partitions, and extend the partition you want to keep into the, now "unallocated" partition reducing it to zero. This is non-destructive to the bulk of the partition that you want to keep.
BTW, within Windows Disk Management you will not see these unwanted partitions. Only C: System Reserved shows there.
Within the "MiniTool", Initialise all your non-C: drives. This is non-destructive also, for you do not format the drive, only change the way BIOS sees the drive. There is a box at the start of the Bar Graphs (on the left). Select, then Right Click it, and choose "Convert MBR to GPT" (Globally Unique ID/Partition Table).
Now your non-C: drives will not conflict with BIOS. The BIOS is looking for that MBR, but unknown and/or unseen "System Reserved/MBR" partitions are confusing the startup.
Do a cold shutdown and reboot to BIOS (del key). It may take several seconds to access.
Now go into BIOS and select each non-C: drive and "disable" each, to make them a non-boot drive. This ensures that BIOS only has one hard drive to seek! The list should only have your C: drive as active boot.
To confirm that your non-C: drives are actually GUID drives, go back to Windows Disk Management. Select the panel at the start of the Bar Graph (on the left) then right click>Properties>Volumes tab.
Here is confirmation about Partition Style. GUID is the future of Drive classification. The 2TB Limit does not apply to Guid Partition Table (GPT).
I hope this works for you, but read up about it, and also read the forums before you act. Make yourself certain that my fix is valid.
The ability to change OS's is not something I have done before.
Sometimes MBR is useful. Partition Styles need some thinking.
