If you have upgraded Windows or reinstalled it without formatting your hard drive, you may notice that there is a Windows.old folder on the C drive (or a your primary hard drive partition). This folder contains files from the previous windows install. The folder is used to back up potentially important personal files or to roll back to the previous OS in case of an installation failure. However, the folder takes up large amount of disk space. If you have personal files in there, you can move them out of the folder, but everything else is pretty much useless. You will want to delete that folder to save disk space. But you need to delete it properly, and we’ll show you how to do just that!

Note that if you are on Windows 8 or Windows 8.1 (or their server and ARM counterparts), most of the content of the folder will automatically be deleted after some time. But you might still want to do a full cleanup. You cannot simply delete it like a normal folder, as Windows will block you from doing so. You will need to use Disk Cleanup.

This will clean up the Windows.old content completely and give you back large amounts of disk space. However, we must launch disk cleanup as an administrator. Follow the steps below, it should work.

Try these steps (in exact order) to remove the Windows.old content:

If you are running Windows 7:

• Step 1: Open the Start Menu and on the search box, type “Disk Cleanup”
• Step 2: Right-click on “Disk Cleanup” and click “Run as Administrator”. You might need to click “Yes” or type your password. Please do that.

Please go to Step 8 below

If you are running Windows 8 or Windows 8.1:

• Step 1: Go to the desktop, either by clicking the desktop tile or by pressing “Windows Key” + D on your Keyboard.
• Step 2: On your Desktop, open the charms. If using touch, swipe from the right edge. If using a mouse, point mouse to lower right corner and pull up. If using the keyboard, press the keys “Windows Key” + C.
• Step 3: Click the “Settings” charm.
• Step 4: Click on the “Control Panel” option.
• Step 5: On the control panel Window, click on the search box and type “Admin”.
• Step 6: On the search result, the first item should be “Administrative Tools”. Click on “Administrative Tools”.
• Step 7: When the “Administrative Tools” folder opens, find the item that says “Disk Cleanup”. Right click on that item, and click “Run as Administrator”. You might need to click “Yes” or type your password. Please do that.

Please go to Step 8 below

 Steps 8-10 works for Windows 7, 8, and 8.1:

• Step 8: On the “Disk Cleanup Drive Selection” dialog box, click OK. Wait for Disk Cleanup to search your hard drive. When it finishes searching, it will pop open the Disk Cleanup Dialog Box.
• Step 9: You will see many entries to check off. Please find the entry that says “Previous Windows Installation”. Click that. You will see how much disk space you will be saving. If you want, you can check off other items too to clear up even more disk space!
• Step 10: Once you checked off the items, click OK to start cleaning your heard drive. This will delete the Windows.old folder and its contents! Warning: Anything on that folder will be deleted!