Installing a pre-installed NIS2009 on other PC's

Hi, sorry I don't know much about all of this.

 

I've just purchased a computer with NIS2009 pre-installed and saw under "mynortonaccount" that i've got "protection for up to 3 PC's". This doesn't seem possible to me. How do I install it on other PC's without the product disc or a product key?

 

Thanks in advance