With most Norton/Symantec products that provide a registration code via Internet, after the Windows install and you reinstall the product, use that same key code and you should have the remainder of your product life. I had to wipe a drive recently and do this with Norton Security Suite. After I went through registration, it informed me that the user had 200+ days remaining, which was the anticipated response.
If not, you can always contact Symantec and they will help.