How to dual boot from two sepoarate drives where Windows 10 and Windows 7 were previously installed separately.

[mikech]

I built a new state of the art computer. I then purchased a license for Windows 10 home edition and installed it for the new computer. Everything works fine.

Then I installed the old Windows 7 boot disk and data disk from the old Windows 7 computer into the new Windows 10 machine. Everything still works fine.

Now that I know there will be no hardware issues I want to choose which boot disk to boot from, the Windows 10 or Windows 7. Is this even possible??

I could of course just leave the back cover off and unplug the Windows 10 boot drive but I don't want to have to do that. Perhaps there are some magic commands that can make the boot process recognize both drives as potential boot drives and give me a choice??

I understand the normal way to create dual boot, where you install another OS after the primary. But this situation is somewhat different.

By the way I have read the other posts that are similar to this but none of those solutions work for me. I know how to do this in any given instance by selecting the bios boot menu during boot up.

But that's not what I am looking for. I will be turning this computer over to a novice. I want a dual boot menu to come up automatically during every boot without having to buy external software for Windows 10.

 

[dgingeri]

If your motherboard has the function, you might be able to hit a key and select which boot device you'd like to use. Otherwise, you'll probably have to change the boot order in the BIOS every time you switch.

 

[noidea_77]

You just add the Windows 7 boot record to the Windows 10 boot loader
https://msdn.microsoft.com/en-us/windows/hardware/drivers/devtest/adding-boot-entries

 

[mikech]

You just add the Windows 7 boot record to the Windows 10 boot loader

That makes sense and that is certainly how I would do it in Linux using Grub. My problem is that I do not know how to do that in Windows.

OOPS! You must have been typing when I responded. I see the link now. Thank you!

 

[noidea_77]

You just add the Windows 7 boot record to the Windows 10 boot loader

That makes sense and that is certainly how I would do it in Linux using Grub. My problem is that I do not know how to do that in Windows.

OOPS! You must have been typing when I responded. I see the link now. Thank you!

Only tricky part: the win 10 boot loader must be the default. Your Win 7 loader doesn't know how to start Win 10 and fails, even if you add the entry.

 

[mikech]

You just add the Windows 7 boot record to the Windows 10 boot loader

That makes sense and that is certainly how I would do it in Linux using Grub. My problem is that I do not know how to do that in Windows.

OOPS! You must have been typing when I responded. I see the link now. Thank you!

Only tricky part: the win 10 boot loader must be the default. Your Win 7 loader doesn't know how to start Win 10 and fails, even if you add the entry.

Thanks!

I am finding out that as usual, Microsoft's documentation is extremely inadequate. I would never risk messing with the boot sector based on the woefully inadequate information, however I found more detailed information at Superuser now that, (thanks to you), I know what I am looking for. I will try to do it this weekend and report back what worked for anyone else in similar circumstances.

 

[dgingeri]

I didn't even know you could do this. Good to know. Thanks.