Moving old Win 10 system disk into Win 11 PC as secondary drive

I've just set up a new old PC (i7-8700) as my first running Win 11. I'd like to move the HD in my old Win 10 PC into this new one as a secondary drive as it holds all my documents. If I do so, will it confuse the bootloader on the Win 11 machine? I want it to boot to Win 11. Thanks.

Follow-up: What if I want to have the option to also boot the old Win 10 system? How would I enable the second drive to also be a boot drive? (I know I'd likely have driver issues, but would like to know anyway.)

Apesbrain said:

I've just set up a new old PC (i7-8700) as my first running Win 11. I'd like to move the HD in my old Win 10 PC into this new one as a secondary drive as it holds all my documents. If I do so, will it confuse the bootloader on the Win 11 machine? I want it to boot to Win 11. Thanks.

Follow-up: What if I want to have the option to also boot the old Win 10 system? How would I enable the second drive to also be a boot drive? (I know I'd likely have driver issues, but would like to know anyway.)

Click to expand...

There's been lots of posts over time where having a second drive in a computer during setup can cause issues if the second drive has or had a former installation of the OS on it. If the second drive was bootable but not wiped clean the booting could be confused. My experience since getting a job in a computer store in '94 and building/repairing computers has shown that installing the OS on an only drive and getting it working is best then add a second drive later. I use a USB Dual-bay drive dock connected to a Linux desktop to copy any files to be saved to another [third] drive then using GPARTED to wipe the original drive clean before using it for additional storage, advantage is the third drive can be saved as an archive.

Berton said:

There's been lots of posts over time where having a second drive in a computer during setup can cause issues if the second drive has or had a former installation of the OS on it.

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In this case, the Win 11 PC has already been set up with a clean install. I'm just moving an SSD from the old PC to the new. Bootloader won't see the second drive at all, right?

If the BIOS can see a drive when the computer is turned on the Operating System will know about it. The OS reads the BIOS to know about the resources available and sets up accordingly such as loading drivers.

When you install the old drive to the new computer it's just another boot able drive on the system.
Probably the new Win 11 drive was set as UEFI-GPT and if the old drive is also set as UEFI-GPT, all you have to do is to launch the Boot menu (F12?) during POST and select the old drive to boot from it.
If the old drive was set as Legacy-MBR, it's a little more complicated as BIOS must be set to boot as UEFI-GPT and Legacy-MBR. In this case I suggest you convert the old drive from Legacy-MBR to UEFI-GPT.

Please edit your profile with ALL your hardware specs. It will help us to help you

Please post a whole window Disk Manager image of ALL your drives. Don't forget to expand the columns so we can read them. How to Post a Screenshot of Disk Management
If you have a MiniTool or AOMEI Partition use it instead or Windows disk manager.

Megahertz said:

In this case I suggest you convert the old drive from Legacy-MBR to UEFI-GPT.

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I did this and moved the old Win 10 drive to the new Win 11 PC. F9/BIOS can see the drive, but will not boot from it when selected. Is there something else I need to do to make this drive bootable?

Apesbrain said:

I did this and moved the old Win 10 drive to the new Win 11 PC. F9/BIOS can see the drive, but will not boot from it when selected. Is there something else I need to do to make this drive bootable?

Click to expand...

The old drive is probably Legacy - MBR so it won't boot as a UEFI - GPT
Please edit your profile with ALL your hardware specs. It will help us to help you
Where is the disk manager image I asked on the previous post?

Megahertz said:

Where is the disk manager image I asked on the previous post?

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Sorry, here it is:



This PC is an HP ProDesk 600 G4 SFF: Win 11P x64, i7-8700, 32 G RAM.

Normally on a Win 10 boot able MBR drive you have a System partition with the boot manager. Why this drive doesn't have it?
On the old computer, there is another drive with the System partition?
How did you converted the Legacy-MBR into UEFI-GPT? Did you converted on the old computer or in the new one?

It doesn't boot because the Win 10 (E:) drive is encrypted and the EFI partition and the boot manager doesn't have the key.
Do you have the bitlocker key for the Win 10 (E:)?
How to unlock a drive on another computer

Megahertz said:

How did you converted the Legacy-MBR into UEFI-GPT? Did you converted on the old computer or in the new one?

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I converted MBR to GPT on the new computer. Actually, I was surprised to see mention of "Bitlocker" as I did not use it on my old PC. I did not know that Win 11 implements Bitlocker by default.

I can read files from this drive, just not boot from it. I can live with that, I guess. Thanks again for your help.

Yes it does, Is what it is called "Device Encryption"
Disable bitlocker on E: so we can try to rebuild the EFI partition.

I've found the setting to turn off BitLocker for that particular drive. Once I've done this, what would be the steps to rebuild the EFI partition? I'd just like to know all that is involved before I decide next steps. Thanks.

Unless you just want a dual boot situation I agree with @Berton. Although I am not as proficient as these other guy in this area, I foresee problems at some point in the future with having 2 drives, each with a different bootloaders on them.

If it were me I would do it correctly by backing up the data I wanted to save on the old drive and reformatting that drive as a storage drive. I would also format the drive as MBR so as to avoid ANY future issues with my windows 11 bootloader being written to the wrong drive by an update, upgrade, or repair or clean install. I'm a firm believer in KISS (keep it simple, stupid)

Then I would be asking myself a few questions about how I intended to use this storage drive before I went any further and before I moved the old files I backed up back onto the drive:
Is it my intention to move the default location of any of my windows 11 user folders to the storage drive? If so do I want to integrate my old data into these folders?
Or do I want to keep all this old data separate from my Windows 11 data?

I don't agree with glasskuter. I think is better to have totally independent drives, each one with its own OS.

Under Win 11 you identify the EFI partition, format and reload the boot manager.

To identify the EFI partition, open a CMD window as administrator and type:

diskpart
list disk (it will list all drives. Identify the Win 10 drive number)
select disk n (replace n by the Win 10 drive number obtained with list disk)
list part
exit

Post the results here.

As I said.... Unless he has a specific need for a dual boot system, then he should reformat. If he does not, and wants a storage drive only, he's asking for trouble in the future having 2 efi partitions in his setup. We've seen doing so cause issues time and time again.

Thanks all. I'll wait a few weeks to be sure I've migrated any documents I need and then reformat the second drive as straight storage.

I'd just like to follow up someone's suggestion above that the drive be reformatted MBR rather than GPT which it is now. That seems like a step backwards to me. Isn't GPT the more "modern" option?

Apesbrain said:

Thanks all. I'll wait a few weeks to be sure I've migrated any documents I need and then reformat the second drive as straight storage.

I'd just like to follow up someone's suggestion above that the drive be reformatted MBR rather than GPT which it is now. That seems like a step backwards to me. Isn't GPT the more "modern" option?

Click to expand...

I've not used MBR for years.

I believe that if you have deleted the partitions on the drive and created a single new NTFS partition with no traces of a former OS installation, a clean Windows install will not put files on it rather than the target drive.

But I do clean installs rarely. More experienced people may have more informed knowledge.

Apesbrain said:

Isn't GPT the more "modern" option?

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Yes it is but here is my reasoning for suggesting it and it is for the exact same reason I am against having an old gpt system disk plugged in without reformatting it.
Always when installing windows, upgrading windows, and even at times a firmware upgrade (depending on the specific device and the nature of the upgrade) the bootloader is written to the first EFI System Partition (ESP) that it encounters, even if it's on a different disk than the main Windows installation. This behavior can lead to issues when multiple disks with EFI partitions exist, as the installer might not choose the ESP on the intended drive depending on how the bios numbers the drives.

I'll give you an example from my own Dell PC. This motherboard identifies my nvme system drive as disk 1. It identifies my sata hdd as disk 0. With both disks configured as gpt, if I do not remove my hdd before I clean install, do an upgrade, or do a system reset, my bootloader writes to the wrong disk.(the HDD) If I lose that HDD, I lose my bootloader so even though the hdd is my storage drive I lose Windows too.
Granted, whether this could happen to you depends on your motherboard and how it's manufacturer has written it's UEFI bios to identify the drives.

The newer GPT partitioning was developed when disks became larger and folks wanted to create more and larger partitions on them.
GPT allows for many more partitions on the disk(128) and can deal with larger disks over 2 tb. MBR works with disks (2tb or less in size with up to 4 primary partitions or 3 primary + 1 extended with multiple logical partitions). Unless a disk is larger than 2tb or one wants to use a bunch of partitions, there is really no need to use GPT if one wants to guarantee their bootloader never gets written to the wrong drive.

So it's fine if you want to use GPT on both/all your drives so long as you understand how it all works together.

Sorry if it is already said, I didn't have time to go through all the posts. You can connect your old disk on your new computer but before booting the first time press DEL (or whatever is the correct key) to enter UEFI firmware (aka BIOS) and make sure the new disk has higher boot priority than the old disk. This means the computer will look at the new disk first and boot into Windows 11 than loading Windows 10. Since Windows 11 is installed by default in UEFI mode (GPT), it should appear as "Windows Boot Loader" at the BIOS. If Windows 10 is also installed in UEFI mode, then you should see two "Windows Boot Loader" entries in BIOS, but they should differ, probably by size, not sure, so you should tell which is which. If Windows 10 is installed in Legacy BIOS mode (aka CSM, MBR) then it should appear by the model of the old disk. In case you want to boot into Windows 10 (CSM) you must enable CSM support in BIOS. Many motherboards allow both UEFI and CSM and you can give higher priority to UEFI, so it will boot Windows 11 first. When you switch on or restart the computer you can press F12 (or F11 or whatever is the correct key) to see the Boot menu. From there you can select to boot either the new disk (Windows 11) or the old disk (Windows 10). In any case, the currently running Windows version will be disk C and the other disk will be the next available drive letter.