Re: I need the reinstall disc as the original is lost on XPS 720
Welcome to the community.
In addition to what RoHe said: once you have the disks then you can check the link below for finding out instructions for re-installing Windows XP.
Also, you would need to download and install the drivers for your system. Please check the link below which would be helpful for you:
If you have any further queries feel free to reply to us.