Everyone knows that if you install Windows 7 or Windows 8 in the form of an unformatted C-disk, such as a direct upgrade or hard drive installation, you will leave a Windows.old folder under C disk. This folder is used to keep old Windows system files, most of which are redundant unless you want to use a dual system. Personal proposal to delete windows.old, to free more space for C disk.
How to delete the Windows.old in the C disk, in fact, the official has a detailed method introduction, the general operation is as follows:
By right-clicking the C disk (system disk, Windows.old partition), click General-Disk Cleanup.
On the Disk Cleanup tab of the Disk Cleanup dialog box, select the previous Windows installation check box, and any additional check boxes that correspond to the files that you want to delete, and then click OK.
Pop-up dialog window "OK to permanently delete these files", click Delete file.
Again, the original Windows.old folder has been deleted, this operation can help you to free up a lot of system space.
Warning: Before using Disk Cleanup, make sure that all files and settings are in the location that you want them to be in Windows 7. The delete operation on the Windows.old folder is not revocable.