How Do I Reformat and Reinstall Windows 11? (2024)

When you need to completely start over.

To reformat and reinstall is considered the "nuclear option" when it comes to dealing with Windows problems (or just cleaning up).

To reformat a computer is the equivalent of erasing a messy chalkboard and starting over with a completely blank slate.

To reinstall Windows is to fill up that chalkboard cleanly with new information. That means erasing the hard disk and starting over with nothing.

Reformat and reinstall

I can’t stress the importance of Step 1 enough. We’re about to erase everything on your hard disk. Unless you know for certain there’s nothing there you need from it, an image backup is the right way to be prepared when you remember some weeks from now that you forgot to save a specific file.

(Re)Formatting

The term formatting goes back to days when hard disks had to be physically prepared before data could be written on them. Formatting set up the underlying magnetic information so the disk could be used. The term also referred to the next step: setting up the initial data to organize the files and folders to be added later. That last step — setting up the initial data on the disk — makes anything that was on the disk inaccessible. As a result, reformatting came to mean exactly that: erasing the disk by setting up new initial data structures.

For the purposes of reinstalling Windows from scratch, all we really care about is that the disk be erased. The easiest approach is to let Windows Setup do that for you. The “trick”, if you want to call it that, is that it’s not always obvious what to do in Windows Setup. So I’ll show you.

Starting setup

The first step is to boot from your installation media. How you do that varies dramatically depending on your specific computer. If your computer has the UEFI BIOS, which includes things like “secure boot”, this article applies. If your computer is older and has a traditional BIOS, check out this article. Once you boot, you’llbe asked to choose your language and keyboard; then click Next.

The setup program will run. If you have a product key, you can enter it here or click on I don’t have a product keyto do so later. Click on Next.

Note that if you’re reinstalling a previously installed version of Windows, you may not need an activation key. Even if you do, it’s OK to click I don’t have a product key. You’ll be asked to activate it after the system is installed and running. Next, select the version of Windows you want to install.

Unless you know otherwise, choose Windows 11 Home or Windows 11 Pro as appropriate.

Click the “I accept the license terms” checkbox, and click on Next.

When asked to choose the type of installation to perform, click onCustom.

Disk operations

Windows Setup will ask where you want to put your new installation. This is where the reformatting magic happens.

The dialog box lists all existing partitions on the hard disk. In this example, you can see that there are several. To perform a complete reformat of the disk, click on each existing partition on the disk you want to install to (Drive 0 in the example above), and then click on Delete for each. You’ll need to confirm the deletion of each.

After all partitions have been deleted, you should be left with only “Unallocated Space” on the drive you want to install to.

In the example above, there are two physical drives in the system. Drive 0 is the system drive, and the drive on which we want to install Windows. It now has no partitions at all.

At this point, Windows Setup formats the drive and proceeds to install Windows normally.