Boot HDD not found anymore after windows 11 install

Hello -

i decided to upgrade to Windows 11 but I kept getting the error that my pc was not ready. I changed my the bios options for UEFI and secure boot.

Obviously because I did not do my due diligence my 3 HDDs were using MBR (so i was not able to boot any of those drives) so after reading up on it i formated one of the drives using a win 11 USB Stick and installed win 11 on the new formatted disk. Which was not the original win 10 hdd that I had used before. So now I could boot the computer and access all disks using the fresh installed windows 11.

The original plan was to switch back to the windows 10 install after i used a program to change my other two hdd from MBR to GPT without loosing any data.

Now i have the problem that my old hdd with the windows 10 installation is not shown as a boot option.

I would like to use the upgrade path with my old win 10 installation because I currently do not have a windows 11 key and i would like to not loose any data on the main drive.

any ideas what I did wrong this time?

You're booting UEFI now, right? When I did that to install Win11 last Fall, I had to change all the other boot drives to UEFI and GPT in order to be able to see them. Your BIOS/UEFI might have the same limitations -- and it might also be related to Secure Boot.

Mark Phelps said:

You're booting UEFI now, right? When I did that to install Win11 last Fall, I had to change all the other boot drives to UEFI and GPT in order to be able to see them. Your BIOS/UEFI might have the same limitations -- and it might also be related to Secure Boot.

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How do I change a hdd to UEFI? I thought it is the way the bios boots the computer....

There are two kinds of boot able drives: Legacy-MBR or UEFI-GPT
If you had a Legacy-MBR and you just converted from MBR to GPT you won't be able to boot because now you have a GPT drive that isn't UEFI.
Legacy-MBR drives boots on a different way than UEFI-GPT.
On a Legacy-MBR, BIOS transfer the boot sequence to a drive MBR that will transfer to a master boot manager. This master boot manager (like Linux Grub) can transfer the boot sequence to a partition (like Linux) or to another boot manager in another partition (like Windows). It is a serial chain mode.
On an UEFI-GPT, BIOS transfer the boot sequence to the BIOS priority boot manager on a Fat32 Partition and then to a OS on a partition (same drive or even to a different drive). On the FAT32 partition you may have one or many boot manager(Linux and Windows etc). It is not a serial chain mode. It is a parallel mode.
To convert a Legacy-MBR to UEFI-GPT you should have used MBR2GPT.
Now it is too late for it. You have to create a EFI Fat32 partition and install the boot manager on it.
Please post a disk manager image (full window and don't forget to expand the columns so we can read them).

Megahertz said:

To convert a Legacy-MBR to UEFI-GPT you should have used MBR2GPT.
Now it is too late for it.

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Not true at all, if @Kroni still has a disk that is MBR with the standard Windows on it. They just can't boot that drive now because they enabled secure boot. But that disk is still eligible for the mbr2gpt conversion if it meets all the other requirements.

NavyLCDR said:

Not true at all, if @Kroni still has a disk that is MBR with the standard Windows on it. They just can't boot that drive now because they enabled secure boot. But that disk is still eligible for the mbr2gpt conversion if it meets all the other requirements.

Click to expand...

This is basically what I did last Fall. I converted one disk to GPT, switched the boot to UEFI, and installed WIn11 on it. Then once up and running, I used MBR2GPT to convert the other two disks. Now all three are UEFI/GPT and the UEFI BIOS sees all of them just fine.

NavyLCDR said:

Not true at all, if @Kroni still has a disk that is MBR with the standard Windows on it. They just can't boot that drive now because they enabled secure boot. But that disk is still eligible for the mbr2gpt conversion if it meets all the other requirements.

Click to expand...

Much easier to delete the System partition and create a EFI and MSR partitions on the space.

Megahertz said:

Much easier to delete the System partition and create a EFI and MSR partitions on the space.

Click to expand...

You cannot create EFI System or MSR partitions on an MBR disk.

NavyLCDR said:

You cannot create EFI System or MSR partitions on an MBR disk.

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I know.
OP has already converted a Legacy- MBR boot able drive into GPT without converting to EFI (It has no EFI partition)

Megahertz said:

I know.
OP has already converted a Legacy- MBR boot able drive into GPT without converting to EFI (It has no EFI partition)

Click to expand...

I needed to reread the OP! You are absolutely correct! My error!