1 vista cd used on 2 pc's help!!!

Hi, okay so i have a vista cd for premium that is being used on another family members computer. I was wondering if i can use this cd on my computer also to use vista instead of needing to buy another copy of vista?

I could do this with xp i had 3 computers running of the same disk.

Also my computer and the other computer are running off the same router and have the exact same ip address so that is probbably why i think i can use the cd on both computers, i can't see how Microsoft could see the difference between 2 computers using the same router and same ip adress.

Thanks for your help

Also i know this is kind of off topic for this thread but which one of these memory's are the best i am using an intel DQ35JO motherboard. I don't plan on overclocking and i already have 2gb of ram i am just adding on ram for vista(if i can use it)

http://www.newegg.com/Product/Prod [...] 6820227231

http://www.newegg.com/Product/Prod [...] 6820227139

http://www.newegg.com/Product/Prod [...] 6820227169

hes right, i bought a xfi sound card and i had to reactivate vista again. its irritating when you simply reformat every 4 months like i use to with xp, i had to call microsoft and do the whole code activation thing to reactivate my legal disk (which insists of entering 9 rows of 7 numbers or some bs) since i had installed it so many times. May seem as an annoyance, but they gota protect their wallets in 1 way or another