I backed up windows 10 to an internal 1 of 2 drives in my computer...well I didn't like the amount of space it used(gb)...can anyone tell me how to undo that action so I can get the space back? Thanks
There's no standard location, you set this location when you set up the backup. But you should know which drive it went to since you know that drive is getting full. You might have to enable hidden and system files to be visible in Explorer.
Go to Settings, Update & Security, Backup. See whether you've used "Windows 7 backup" app.