Question Can't boot to windows without CSM enabled after changing to GPT

DerekForDayz

Reputable
Dec 29, 2016
15
0
4,510
0
Hey everyone,
I converted my boot drive to GPT from MBR, and the drive shows as GPT in disk management.
All seems good, until I go into the bios and disable CSM, and none of my drives then show up to boot to.

I would really appreciate any help with this, thanks!

 

DerekForDayz

Reputable
Dec 29, 2016
15
0
4,510
0
The boot partition is still disk 0, you may have made Disk 3 into GPT which is C but the PC boots off the partition marked System & in an MBR situation, its also marked as Active.
I see, so is there a way to change the disk number of my windows ssd or is there something else I should try? Thanks again
 

Colif

Win 10 Master
Moderator
Step 1. Boot your computer from a Windows installation disc or recovery disk. Press Shift+F10 in the setup to enter command prompt window.

Step 2. Run the commands below to shrink a partition to get unallocated space.

  • Diskpart
  • List disk
  • Select disk X (X represents the disk number of the disk that needs an EFI partition)
  • List partition
  • Select partition N (N represents the partition number of the partition that needs shrinking)
  • Shrink desired=500 (shrink the partition by 500MB)
Step 3. Then you can create EFI partition using unallocated space with the command below:

  • create partition EFI size=200
  • format quick fs=fat32 label="System"
  • create partition msr size = 128
Step 4. After those two partitions have been successfully created, use the commands below to install boot loader and other applications needed.

  • bootrec /fixboot
  • bcdboot c:\Windows /s b: /f all
Step 5. Reboot your computer to see if it is fixed.
https://www.diskpart.com/windows-10/missing-efi-partition-windows-10.html
that should fix it, will need to go into bios after and change boot method
 

Colif

Win 10 Master
Moderator
this is partially why i let other people do these...
diskpart
list disk
select disk 3
list vol
select volume no.
[NOTE– Replace the “<volume no.>” which is declared to have 100 MB storage. This partition contains the EFI (Extensible Firmware Interface) and usually formatted in FAT32 format.
assign letter=v
exit


now type this
v:
bcdboot C:\windows /s V: /f UEFI

 

DerekForDayz

Reputable
Dec 29, 2016
15
0
4,510
0
this is partially why i let other people do these...
diskpart
list disk
select disk 3
list vol
select volume no.
[NOTE– Replace the “<volume no.>” which is declared to have 100 MB storage. This partition contains the EFI (Extensible Firmware Interface) and usually formatted in FAT32 format.
assign letter=v
exit


now type this
v:
bcdboot C:\windows /s V: /f UEFI

“Failure when attempting to copy boot files.”
Man this is going great. I looked up a few solutions to this and they said to set the drive as active, but I can’t due to it being non-MBR. Would reinstalling windows honestly be a better alternative to this?
 

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