Renewing a subscription

My subscription will shortly be coming up for renewal.

 

I have upgraded from NIS 2009 to 2010 - no problem. It appears that NIS 2009 is available for far less money than what Symantec is charging or that others are charging for NIS 2010. My impression is that all one needs is that magic "secret code" or serial number to activate a subscription and with that code one is entitled to the most recent version of NIS.

 

My question is: If I purchase a single user, 3 PC license for NIS 2009, will I be able to extend my subscription of NIS 2010?

 

One other question: I find some vendors offering NIS for really cheap money via download only (like less than $20 for a 3 PC license). Are these sites legitimate in that they are providing legal serial numbers?