If you updated Windows 10 to the latest build you're going to notice that it created a Windows.old directory on your local disk that takes up a lot of disk space. The build in Windows 10 Disk Cleaner won't make it possible to remove everything. There's still a few Intel Trusted Installer driver files that can't be removed.
If you want to remove every Windows.old file from your GPD Win local disk to regain disk space you can use the Delete Windows.old tool that you can download here: http://download.cnet.com/Delete-Windows-old/3000-2094_4-76456045.htmlLooks like it doesn't delete the Trusted Installer files but puts it in a new folder.2,
Use the Advanced Boot options in Windows 10 and let it restart to Boot the Commamnd Pronpt. Follow this guide here: http://www.thewindowsclub.com/delete-remove-windows-old-folder
Although it didn't recognise the command cacls
and the second commamnd did nothing it did delete Windows.old with the third command line.