Hello,
My online backup (45 GB) is full. so I want to delete these backup sets and start again how do I do this?
Hi ianconstable.
Welcome to the Norton Community Forums. 
Sorry about not replying before but I have only just notice your post.
There should be two ways that you can do this.
The first is to open the backup pane, select the backup set that you want to delete and then select "delete backup set" then when you get the option of just deleting the set (i.e. the definition of the set) or the set and the files, select set and files. This should work but may take a long time.
The second is to open Windows Explorer and look at the Norton Backup Drive. There you should see all of your online backup sets with black globe icons. Right click on the relevant icon and select Delete. This may also take some time but is likely to be quicker I believe.
I hope that helps.
Do let us know how you get on.