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I have prepared installers for both operating systems
The Windows 11 operating system installer is a red USB stick, a blue USB stick is used to install Windows 10 operating system
I plugged the red USB stick into the target computer and started to install the Windows 11 operating system
How to install Windows 11 operating system like you install an operating system for your computer
In this example I install Windows 11 without a Microsoft account
If you want to install Windows 11 without using a Microsoft account, open a command window with Shift F10
Then you enter the command oobe\bypassnro to bypass the requirement to enter a Microsoft account when installing Windows 11
Please note that the target computer's Internet connection is disconnected when installing using a local account
I install Windows 11 operating system on the whole hard drive
I will create a new partition to install Windows 10 operating system after installing Windows 11 operating system
Because I install Windows 11 on the entire hard drive, I need to create a new partition to install Windows 10
On Windows 11 I open the drive manager and create a new partition
In this example I use a solid state drive of size 60 GB to install the operating system which is something I do not recommend
Because it is so small in size, in practice you should use a hard drive of at least 120 GB to install both operating systems.
Now I remove the red USB stick and plug the blue USB stick into the target computer to install Windows 10 operating system
You can refer to how to create Windows operating system installers on the internet to create USB sticks like this
In UEFI I set up the computer to boot from a USB stick
I install both operating systems on the same hard drive with two different partitions
Please note to install Windows 10 on the partition created in the previous step
There is an unformatted partition here, which is the partition to install Windows 10
I just selected it to install the second OS on the target computer
You will see that every time you start the target computer, the operating system options will appear
For Windows 10 I also use a local account when installing
Default operating system to boot is now Windows 10
Wait until the Windows 10 installation is complete I will change the default operating system settings on startup
I will skip some familiar steps when installing Windows 10 so you don't have to wait long
I have finished installing both Windows 11 and Windows 10 operating systems on the same computer
As mentioned the target computer will be booted by default as Windows 10, so how to change that
You restart the computer and set up as follows
The default timeout is 30 seconds so it's too long I will set the timeout to 5 seconds
Next I changed the default boot OS to Windows 11
Because in fact I use Windows 11 more than Windows 10
Above are the basic steps to install Windows 11 and Windows 10 on the same hard drive
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