Windows XP Professional

hello my next door neighbours xp home edition had gotten corrupt thrugh some sort of virus and i have a xp proffesional cd for it to change it from home to professional but the problem is ive stuck the cd in not knowing the code and since his computer is screwed it wont even start so it goes straight onto the windows xp instalation process but i havent got the product key for that disk can any of you help me by giving me a valid product key or something along the lines of helping me at all? thanks