How do i find my product code when i’m installing xp on a fresh computer?

I’ve just built a brand new computer and i’m installing a new copy of windows xp. It’s a legitimate copy which hasn’t been used before (still sealed), but i don’t have the code with it. How do i find the code for the disc, i’m currently installing it on my hardrive so it’s still in the basic mode as there isn’t a previous OS system on the computer. What should i do?

Tim