If you upgraded to Windows 8.1 from Windows 8.1 Preview or to Windows RT 8.1 from Windows RT 8.1 Preview, some files used by your previous version of Windows will be left in the Windows.old folder. These files will be automatically removed within 28 days of upgrading, or you can use Disk Clean-up to remove them yourself.
Before you use Disk Clean-up, make sure that all of your files and settings are where you expect them to be. Deleting the Windows.old folder can't be undone.
Open Control Panel by swiping in from the right edge of the screen, tapping Search (or if you're using a mouse, pointing to the upper-right corner of the screen, moving the mouse pointer down, and then clicking Search), entering Control Panel in the search box, and then tapping or clicking Control Panel.
In the Control Panel search box, type Admin, tap or click Administrative Tools, then double-tap or double-click Disk Clean-up.
If you're prompted to choose a drive, select the drive that you've just installed Windows on, then tap or click OK.
In the Disk Clean-up dialogue, tap or click Clean up system files.
If you're again prompted to choose a drive, select the drive that you've just installed Windows on, then tap or click OK.
Tick the Previous Windows installation(s) checkbox, and any other checkboxes for the files you want to delete, then tap or click OK.
In the message that appears, tap or click Delete files.
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