Restoring Dell to original factory settings

Hello,
I have a Dell XPS Gen 5 Dimension desktop which I want to restore to its original factory settings (not just restore to an earlier time). The decision has been made, I've already backed up my data.

The problem I have is that the computer is not reading the cd drives right now, in fact I can only get it to work in Safe Mode. I've gone into the bios and tried to configure it to boot from the CD drive but to no avail, it simply won't read the cd drive. Therefore I cannot use my original restore disk which came with the computer when I bought it.

This is a Dell from 2005 and it does not have an F11 option, only F2 for Setup and F12 for Boot Menu. Does anyone know how else I would be able to get this computer restored to its original factory setings? Your advice is much appreciated.