When you perform an in-place upgrade on a desktop Windows operating system, the upgrade process creates a folder called Windows.old, which you can see in the figure below. A Windows.old folder is also created during some large updates, such as this month’s Windows 10 Fall Creators Update. So what is this folder, can you do anything useful with it, and how can you get rid of it?
The Windows.old folder can trace its roots all the way back to Windows Vista. Ever since the introduction of Vista, in-place upgrades of the Windows operating system result in the creation of a Windows.old folder. This folder contains a full copy of the previous operating system.
How is Windows.old used?
Even though Windows retains a full copy of your PC’s previous operating system, the system is not set up to use a dual-boot configuration. The operating system that was installed during the upgrade is the PCs only bootable OS. Microsoft does not provide a way to boot the PC from its previous operating system. Even so, the Windows.old folder does have a couple of uses.
One use for the Windows.old folder is file recovery. If you take a look at the figure below, you can see that Microsoft does allow you to browse the contents of the Windows.old folder. Within this folder, there are subfolders including things like Windows, Users, Recovery, Program Files, and Program Files (X86). These are the same folders that Windows Setup creates during the Windows installation process.
Normally, if you do an in-place upgrade, applications, documents, and other objects should be automatically added to the new operating system. Even so, I have occasionally seen situations in which an operating system upgrade did not go quite as smoothly as it should have. In these cases, it is sometimes possible to use the contents of the Windows.old folder to fix a botched installation. For example, I have heard stories of administrators retrieving device drivers from the Windows.old folder and using those drivers to enable hardware that was not properly recognized by the new operating system.
The other use for the Windows.old folder is that you can use it to recover from an operating system upgrade that just didn’t go quite the way that it was planned. If after upgrading to a new version of Windows things aren’t working quite right, or you just decide that you don’t like the new OS or major update, you can roll the system back to your previous operating system or Windows 10 build.
Before I show you how to do this, I need to point out that although using Windows.old normally works pretty smoothly, there are no guarantees. As such, it is always a good idea to create a full system backup prior to performing an in-place upgrade. That way, you will have a second option for reverting the machine to its previous state in the event that Windows.old does not work correctly.
So with that said, let’s take a look at how to roll back a system that was upgraded to Windows 10. Begin the process by going to Settings, and then click on the Update & Security option. Next, click on the Recovery link, located on the left side of the Windows Update window.
If you look at the figure below, you can see that the Recovery screen contains an option to go back to Windows 8.1. In the screenshot below, you see that Windows is smart enough to know that I upgraded to Windows 10 from Windows 8.1, and it provides a way of going back to Windows 8.1 by using the contents of the Windows.old folder. If I had upgraded from Windows 7, then the Recovery screen would display an option to go back to Windows 7. In the case of where a Windows.old folder is created during a major update like the Fall Creators Update, you will see the option to “Go back to the previous version of Windows 10.” For the purposes of this tutorial, we are going to assume you went from Windows 8.1 to Windows 10.
Click on the Get Started button, and you will be taken to a screen on which Microsoft asks why you are going back. For example, you can specify that apps or devices don’t work, or that Windows 8.1 was easier to use. Click Next, and Windows 10 will offer to check for updates in hopes that an update might fix your issue, and entice you to stick with using Windows 10. If you click No Thanks you will see a What You Need to Know screen like the one shown below. This screen explains what you can expect from the rollback process.
Click Next and you will see a warning message telling you to make sure that you know your Windows 8.1 password (which may be different from your Windows 10 password). Click Next one more time, and you will see a screen that says Thanks for trying Windows 10. Now, just click on the Go Back to Windows 8.1 button, as shown in the next figure, to revert the system back to your previous operating system.
Getting rid of Windows.old
Although you can use the Windows.old folder to revert to your old operating system, most of the time the Windows.old folder just takes up space. Unfortunately, you can’t delete this folder using conventional means, even though it may be taking up many GB of space. To get rid of an unwanted Windows.old folder, open File Explorer, right click on the C: drive, and choose the Properties command from the shortcut menu. When the C: drive’s properties sheet is displayed, click on the General tab and then click the Disk Cleanup button, followed by the Clean Up System Files button. After several minutes, you will see a screen asking you what files you want to delete. There is an option about half way down the list called Previous Windows Installations. Choosing this option will remove the Windows.old folder.
Keep in mind that Windows will delete the Windows.old folder itself after a certain number of days. For example, the Windows.old folder created during an upgrade from Windows 8.1 to Windows 10 is automatically deleted after 30 days. But the Windows.old folder created after the Fall Creators Update will be deleted after only 10 days.