Can't delete N360_BACKUP

Hi!

Urgently need help here - placed backup in D drive and now it's taking up around 300 GB in my laptop. No option to edit backup settings (all grayed), couldn't delete the file - it just keeps recycling. I've tried using command prompt but access denied, and for some reason can't uninstall Norton neither. Can anyone please help? I can barely use my computer right now. Thanks!