How to remove Windows.old
When you upgrade to each new build of Windows 10 Preview, the operating system automatically creates a backup of the current version and stores it in the Windows folder.old in the root of the system drive. Because of this you can always go back to the previous build, but this could be a lack of disk space, because the backup takes 10 or more gigabytes of precious space. In particular, I have Windows.old used 20.1 GB of hard disk space.
To remove this directory it is possible (and recommended) using the standard tool «disk Cleanup» and clicking «Previous Windows installation».
So, open computer, right-click the mouse icon on the system disk and select Properties >» disk Cleanup».
When you run disk cleanup you may be a little puzzled by the small number of available options, in particular, the lack of option to remove previous installations of Windows under «files to Delete».
This is normal. Simply click «Clean up system files» to the cleanup program again assessed the amount that can be released with respect to the system of files that can be deleted without affecting the operating system.
Once this process is complete, you will see additional options, including the option to remove previous installations.
Select the files and click «OK» to delete them.
In the process, you will be informed about what you are going to remove the previously installed version of Windows.
If you delete previous Windows installations and temporary installation files, will no longer be able to roll back the machine to a previous operating system. Are you sure you want to do this?
Click «Yes» to confirm your decision and continue.