Windows.old can be safely removed.
Windows.old can be safely removed.
I’d retain them for the possibility of reverting. Without that directory and its files, you can’t recover Windows to the previous operating system, so you’d need a full reinstall.
Consider downgrading only if you dislike Windows 10, as many people are likely returning to older operating systems at this time.
You can delete files via Disk Cleanup on the drive. Click right-click, choose Properties, then Disk Cleanup. After the window appears, pick System Files and choose Old Operating Systems. This method is suggested but will prevent you from restoring to Windows 7/8/8.1.
Reflect your current operating system's appearance. Remove any unnecessary files and settings from the OS drive if they're not required. Returning to the prior OS is possible, but a fresh installation will occur. You may relocate the folder to an HDD or backup storage device.