3. If you can see them what happens when you try to delete them?
4. Have you installed Malwarebytes?
Arent these quarantined files from Combofix . So their deletion is not, I suggest, an issue from a Symantec product. Usually removing combofix removes the quobox. Have you uninstalled Combofix?
If you are not happy with that then there are tools such as Unlocker Freeware but I dont think I should go any further as I am surely off topic.