How to do a clean install of Windows 11 using an ISO file

How to do a clean install of Windows 11
(Image credit: Microsoft)

Want to know how to do a clean install of Windows 11? The obvious solution is to sign up for the Windows Insider Program and download the latest build that Microsoft makes available through Windows Update.

However, this method only allows you to upgrade to Windows 11 from your current Windows 10 installation. Although upgrading preserves all your files, settings, and programs, it also means that any junk, broken registry entries and performance issues will be transferred to your new setup. 

Performing a clean install, in contrast, gives you a completely fresh start with Windows 11, and ensures that it runs as smoothly as possible. You can either install the new operating system on a spare PC, or on a partition on your current hard drive, so you won’t overwrite important files or lose access to Windows 10.

There’s been a lot of controversy about Windows 11 requirements, with Microsoft deeming many processors incompatible with the new operating system. The good news is that preview releases of Windows 11 can be installed despite the restrictions, and will work for the moment, at least.

Here we’ll explain how to bypass the Windows Insider Program, and download the latest version of Windows 11 to clean install on your PC. You won't even need to enter a Windows product key.

How to do a clean install of Windows 11: Download the latest build 

The only official way to test drive Windows 11 is to sign up for the Windows Insider Program and upgrade from Windows 10. Microsoft has now released ISO files of the new operating system, but you'll need to be an Insider to try this method.

Fortunately, if you want to clean install Windows 11 without becoming an Insider, it is possible to download ISOs of the latest builds from a third-party website called UU Dump. This is a safe, trustworthy source, and you don't even need to register with the site.

Here we show you how to clean install Windows 11 by downloading the correct ISO file for your PC.

1. First, head to UU Dump, where you can download the latest builds of various Windows versions for free. Click the Dev Channel link at the top of the page. 

how to clean install Windows 11 - dev channel

(Image credit: Tom's Guide)

2. Select the most recent version of Windows 11 at the top of the list of releases.  

Choose the “x64” build, rather than “arm64”, unless you have an ARM-powered laptop such as the Microsoft Surface Pro X.

how to clean install windows 11 - x64 build

(Image credit: Tom's Guide)

3. Click Next on the following page and select the edition of Windows 11 you want to clean install. We chose Windows Home, because that’s the version we’re running on our laptop. Click Next again to confirm.

how to clean install Windows 11 - windows home

(Image credit: Tom's Guide)

4. Select the download option “Download and convert to ISO”. This will make the downloaded Windows 11 build easier to clean install. Also check the box to “Include updates."

Click the "Create a download package" button to download a ZIP file containing the Windows 11 setup files. 

how to clean install Windows 11 - download

(Image credit: Tom's Guide)

How to clean install Windows 11: Create the ISO file 

Once you’ve downloaded the latest Windows 11 build, you’ll need to install the required files to create an ISO disk image of the operating system. The package you downloaded from UU Dump will do the hard work for you.

Here we explain how to perform the ISO creation process and why you’ll need to be patient to get your clean install of Windows 11.

1. Open the downloaded ZIP file and extract its contents to a folder on your PC. The default folder will have a very long name and be located in your Downloads folder, so you may want to create a dedicated folder on your Desktop for easier access. 

We’ve called our folder “win11iso”. Make sure your folder doesn’t have any spaces in its name, as this will prevent installation. 

how to clean install Windows 11 - iso file

(Image credit: Microsoft)

2. Double-click the file in the folder named uup_download_windows. If Windows displays a SmartScreen security warning, click More info and choose Run anyway (the file is completely safe to run.)

how to clean install Windows 11 - run anyway

(Image credit: Microsoft)

3. A command prompt window will now open and start downloading all the installation files required to create the Windows 11 ISO. 

Be warned that this can take a long time, and may hang for a while: we waited for over an hour on our HP laptop.

how to clean install Windows 11 - command prompt

(Image credit: Microsoft)

4. Once all the files are downloaded, the ISO file should be created automatically. Press 0 on your keyboard to close the command prompt window and look in the setup files folder from step 1. 

You should see the new ISO disc image file in the same folder as the uup_download_windows file you double-clicked in step 2.

how to clean install Windows 11 - iso file

(Image credit: Microsoft)

How to clean install Windows 11: Create a bootable install disk 

Now comes the tricky task of creating a bootable install disk from the Windows 11 ISO file. You’ll need a USB stick with at least 8GB of storage space on it.

Usually, we’d recommend using the excellent free program Rufus to create the bootable USB drive, but sadly Microsoft has made this difficult, in fact impossible, with Windows 11.

If you try to burn the Windows 11 ISO to a USB stick using Rufus or a similar program, it will create an NTFS-formatted drive rather than a FAT32-formatted one. This is because the Windows 11 installation file is larger than 4GB, which is the maximum size supported by FAT32.

To boot into a clean install from an NTFS drive, you’ll need to disable your PC’s Secure Boot feature, and Windows 11 won’t run without Secure Boot being enabled. Luckily, there is a workaround, as we’ll explain below.

1. Insert your USB stick and make sure there’s nothing important stored on it, as all data will need to be erased to create the bootable install disk. 

Open the Disk Management Tool by typing “disk partition” into the Start menu search box and selecting "Create and format disk partitions."

how to clean install Windows 11 - disk partition

(Image credit: Microsoft)

2. Select your USB stick in the list of drives, then right-click each of its partitions in the bottom section of the window and choose Delete Volume. Click Yes when asked if you’re sure you want to continue.

how to clean install Windows 11 - delete volume

(Image credit: Microsoft)

3. Next, right-click the USB stick’s empty space and choose New Simple Volume. Create a new partition that’s 1GB in size and format it as FAT32

Create a second partition that uses the remaining space on the drive and format it as NTFS.  

how to clean install Windows 11 - fat32

(Image credit: Microsoft)

4. Once this is done, go back to the Windows 11 folder, right-click the ISO file and choose Mount.  

how to clean install Windows 11 - mount iso

(Image credit: Microsoft)

5. When the ISO folder opens, copy all the files and folders, except the "sources" folder, to the FAT32 partition on the USB drive

Create an empty folder called "sources" on this FAT32 partition and copy the “boot.wim” file from the original "sources" folder into it. 

how to clean install Windows 11 - sources folder

(Image credit: Microsoft)

6. Now copy all the files and folders from the ISO, including those you copied before, to the NTFS partition of the USB stick

This can take a while, but once complete, you should (finally!) have a bootable install disk for Windows 11.

how to clean install Windows 11 - ntfs partition

(Image credit: Microsoft)

How to clean install Windows 11: Perform the clean install

With that difficult part out of the way, you can now perform your clean install of Windows 11 from the bootable install disk on your USB stick, so make sure it’s inserted in your PC.

In our instructions below, we’ve recommended selecting your USB drive in Windows 10’s Advanced Startup Options, but you could also boot straight from the USB stick by changing the boot order in your system’s BIOS. 

1. Restart your PC into Advanced Startup Options. To do this, hold down the Shift key on your keyboard when you choose Restart from the Power menu. 

Alternatively, open Settings, choose Update & Security, then Recovery, and click "Restart now" under "Advanced start-up". 

how to clean install Windows 11 - advanced startup

(Image credit: Microsoft)

2. When the Advanced Startup screen appears, click "Use a device" under "Choose an option."

On the following screen, select the USB stick that you copied the Windows 11 ISO to. As you created two partitions, you’ll see two options: the top one should be the NTFS-formatted partition, so click that. If it doesn’t work, try the other option.

how to clean install Windows 11 - use device

(Image credit: Microsoft)

3. The Windows Setup screen will now open. Choose your preferred language, time and currency format, and keyboard and input method from the drop-down menus and click Next. 

On the following screen, click "Install now."

how to clean install Windows 11 - windows setup

(Image credit: Microsoft)

4. You may now be asked to enter your Windows product key. If you have your license key for Windows 10 to hand, type it in, but if not don’t worry: you can just click “I don’t have a product key” to continue.

How to clean install Windows 11 - product key

(Image credit: Microsoft)

5. Windows Setup will now ask which type of installation you want. To perform a clean install, rather than an upgrade, choose "Custom: Install Windows only (advanced)."

This will mean losing all files, settings, and applications stored on the installation drive, so make sure you have everything backed up.

how to clean install Windows 11 - custom install

(Image credit: Microsoft)

6. Select the drive or partition you want to install Windows 11 on. Obviously, make sure you choose the correct one, so you don’t overwrite anything important. Click Next to continue.

how to clean install Windows 11 - where to install

(Image credit: Microsoft)

7. The clean install of Windows 11 will now begin - at last! Once the installation is complete, you’ll be prompted to restart your PC, so you can enter the exciting new world of Microsoft’s latest operating system.  

how to clean install Windows 11 - installing

(Image credit: Microsoft)
Robert Irvine

Robert Irvine was previously the How-To Editor at Tom's Guide. He has been writing tutorials about software, hardware, websites and other tech topics since the days of dial-up modems, and was previously the editor of Web User magazine. Robert enjoys cooking, and makes a mean sausage casserole, but is definitely not the celebrity chef of the same name.

  • Coneydub
    Hey, I got to the part where I was making the boot disk and somehow I'm NOT getting the option to "Use a device" at the very end when we're restarting our pc with advanced startup repair by holding shift right before the initial windows setup screen. Also, when I try booting to that disk forcibly in my BIOS, it doesn't seem to do anything and just ends up defaulting to my normal Windows 10 hard drive. I can take photos if you need them, but I cant screenshot the bios and/or startup repair menu.

    I followed the instructions really carefully, I even went back and did it 2 or 3 times to make sure I wasn't doing something wrong. I assume there is a bad setting in my BIOS, but I have no clue, do you guys? I did 1024 in FAT32, I think the only thing I changed was I named them every time instead of defaulting "new volume" I named them things like FAT32 and 32 and FT32 and NTFS and FS on the remainder. I just did the "quick format" option the first 2 times, but I eventually used the partitioning in disk management to format the whole thing, make the two partitions, and do a full format with the quick option turned off. Is there something I'm missing? I have an Asus H97M-Plus mobo and I have been futzing a lot with the settings recently to get a new m.2 hd working because NVME came out after the mobo was manufactured; therefore, my never upgraded BIOS didn't have support for something that didn't exist yet at its creation. Not even mother boards can predict the future.

    So how come I cant find that "Use a device option?" I know the drive is plugged in because the win 10 recognizes it. I know the mobo kinda sees it because it shows up in boot priority override section of bios with all the other connected drives. Here is a pic of Disk 4 formatted exactly as asked

    Then here's all the files on them

    What gives, any idea?