Windows XP home volume license key

Hello friends,

I don't know how recently my friend had got genuine license key for his computer when i asked him about the same he told me that it's available very easy on internet i have try to entry his license key on my Windows XP home i got a message as invalid key and when i told my friend to find it for me he was not able to find it. Can anyone provide me a genuine license key for my Windows XP home, i would really appreciate that person.