After upgrading to Windows 10, you may have noticed the Windows.old folder in your C: drive. This important folder lets a user roll back to a previous version of Windows, but it also takes up lots of space, which can be a problem for those with small SSDs. If you’re sure that your Windows upgrade went well and that all of your programs and files are accounted for, here’s how you can delete the Windows.old folder to save precious space on your Windows PC.