I have a re-installation disk from a new Dell Vostro

and I have an old computer ALREADY installed with windows xp. It doesn't have the reset to factory setting installed on the hard drive, instead it asks for me to insert a CD to proceed. Can I use this different disk on the old PC? 

If it asks for the Product Key, I can just use the same old one on the side of the computer right?

This is my first time Reseting Computer to Factory Settings