installing norton on other PCs?

Hi just wondering if someone can help with this query.  I have Norton on my home pc and laptop, but tried to install in on to a new laptop (so 3 pcs in total) and it came up with error saying "...exceeded number of installs..."  So I checked my details on my a/c and seems I only have licence for 1 install.  But if I were to buy online (ie not having renewed automatically) then I would be able to install norton on up to 3 pcs.  Surely I don't have to buy another key at a cost of nearly £40???  Does anyone know what I should do?