Genuine KEY product,

Hi I have borrowed my friends xp home editon disc after having a bad virus, because my xp came built in but i have the key code on the side of my tower, have reinstalled from scratch, but have no sound or can not plat dvd’s or cd’s, with windows media polayer, in my system info its got a Yellow ? by multimedia Audio Controller, and windows is saying its not a genuine disc is this because i borred my friends disc, is there any way i can down load xp home editon and then start again with my key number from side of tower, please,