For most people, running just one operating system on your PC or laptop will be enough. You’ll have to decide between Windows 10 and 11, but you probably don’t need them both on the same device.
However, there are some situations where that might be useful. They include specific apps that haven’t been updated for Windows 11 or only work with Windows 10, or to offer an easy comparison between the two on your hardware.
Fortunately, Windows is designed with this scenario in mind. Running two versions of Windows on the same device is known as dual booting, and it’s officially supported by Microsoft.
Here’s how to run the two latest major versions of Windows on the same device, although this method also works if you can download a different operating system.
What do you need to dual boot Windows?
There are a few things to sort before you begin. The first is to download the second operating system you need – both Windows 10 and Windows 11 are available for free from the Microsoft website. Just make sure you go for the option to create installation media, and buy a product key if you plan on using it long term.
You’ll also need a USB stick or other external storage device with enough space to comfortably store a full operating system.
And as always, it’s important to back up your data using reliable software first. There’s no guarantee nothing will go wrong, so it’s not worth taking the risk.
Before we get to the details, here are the basic steps you’ll need to take:
- Install a new hard drive, or create a new partition on the existing one using the Windows Disk Management Utility
- Plug in the USB stick containing the new version of Windows, then reboot the PC.
- Install Windows 10, being sure to select the Custom option.
- Select the newly created partition or the other hard disk as the destination for Windows 10. Then click Next to install the operating system.
How to install a second copy of Windows
If you’ve bought a second hard drive or are using a spare one, you can install the second copy of Windows to this drive. If you don’t have one, or you can’t install a second drive because you’re using a laptop, you’ll need to use your existing hard drive and partition it. The process is identical on both Windows 10 and 11.
Create a new partition
If you need to install a second version of Windows on the same hard drive as the first, there needs to be enough free space. This can be tricky if you’re running low on storage, as Windows 10 and 11 ideally requires around 20-25GB (and we recommend at least 50-100GB).
Once you’ve backed up any files that are important you’ll need to go to the Windows Disk Management utility. To do so hold down the Windows key and press R. This opens a box, into which you type diskmgmt.msc and press enter.
You’ll now see a list of the partitions on your hard drive. Select the primary partition, usually called (C:), and then right click and select Shrink Volume.
Now you’ll see another window that shows you the size of the partition, and asks you to ‘Enter the amount of space to shrink in MB’. To create a 25GB partition you’ll need to enter 25000 then click Shrink. This will modify the partition, allowing you the space you need to install Windows 10 or Windows 11.
Install Windows onto new partition
Plug in the USB or storage device with Windows on it, then reboot your device.
You should be taken straight to the installation process, but if your machine goes back to your original version of Windows straight away you’ll need to adjust the boot sequence in your BIOS.
This usually means hitting one of Delete, F2, F10 or F11 when your device is turning on (it varies by device), then moving the storage device to the top of the boot priority list. Learn more in our separate article on how to boot from USB.
If successful, you should see a screen which looks like the below. Select the Custom option.
When asked where to install Windows, choose the one labelled as ‘Unallocated Space’ – it should be 25GB, or whichever capacity you specified when creating the partition. Click ‘Apply’, then ‘Next’ once the partition has been created.
Note: if you’re using a separate hard drive or SSD rather than the one built into your device, choose that instead.
Wait for a few minutes while the installation process takes place. Once complete, you’ll be offered the choice between the two operating systems each time you turn on your device.
Both Windows 10 and Windows 11 also use the same file system, so you’ll be able to access all of them them from either operating system.
Now the installation process will continue and finish. The next time you power on or reboot your machine you will have the option to choose between the two operating systems. The bonus is that as different versions of Windows still use the same file system, you’ll be able to access your files from either OS.
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Author: Martyn Casserly, Contributor
Martyn has been involved with tech ever since the arrival of his ZX Spectrum back in the early 80s. He covers iOS, Android, Windows and macOS, writing tutorials, buying guides and reviews for Macworld and its sister site Tech Advisor.