In your settings, there is an option to include your system image. For me, the system image was about 80-90 GB, I think. Your hard drives don't have that much space.
To disable the backup of the system image and remove the errors, go to Backup and Restore, change settings, select the hard drive you want to back up to, select let me choose, and uncheck the system image option at the bottom. Now, Windows will back your files up without any error.
