Attempted Windows 10 Upgrade

Help !!

I recently attempted to upgrade my version of Windows 7 to Windows 10.  After successfully completing the upgrade, I found my system was running very slow in almost every way.   I options to go back to my previous version of Windows 7 and found my Norton Internet Secuirty would no longer work.  I keep getting the message " Your Trial Version of Norton has Expired". 

How do I get my Norton activated again without having to purchase another license ??

Any assistance would be greatly appreciated.  :)