sfjnet

I need to reinstall my copy of Office 2000 but my original Disk 1 is damaged and can't be read. I have a friend who can lend me his disk for the reinstall but the question then arises about the CD/Product key. I have the product key for my original installation but I'm wondering now whether if I use a different disk this key won't work. My friend can probably find the key for his disk but I'm also not sure whether this would work on my PC? Sorry if this is a very junior question but any advice would be gratefully received.