Deleting Windows.old folder from System Drive
Windows.old folder is created when you upgrade your windows to a higher version. This is meant for roll back purpose. If you think that if you are not going to roll back to previous version, you can delete this folder to save much disk space. Windows.old folder is also created if your installation failed and you tried to install windows again in same drive without formatting.
Here is how to delete windows.old folder. Deleting the Windows.old folder can’t be undone.
Open Disk Cleanup by clicking the Start button, in the search box, type Disk Cleanup (or cleanmgr.exe), and then, in the list of results, click Disk Cleanup.
Disk Cleanup window will open. Click Clean up system files.
The tool will check for any old windows and will display in a new window. Select Previous Windows installation(s) and click OK.
If you get any prompt that ‘You cannot restore the machine back to the previous version of Windows’, click Yes.
The cleaning process will begin. This process may take some time.
Once the operation is completed, you can check disk space of your System Drive. All the old Windows installations are deleted.