Presuming you are the registered owner of the computer you can request backup disks at this link:   [URL]   Yes, you can download the necessary drivers as you suggest above, but unfortunately all the possible drivers for your system will be listed for all possible configurations, not just the drivers specific to your personal system.  Dell is supposedly working on updates to their system to only list the specific drivers for a given computer, but I don't believe that has occured yet on most systems.  The next link gives information on driver installation following a reinstall: [URL]  
Hello Recently I was given a brand new XPS 420 and it comes with no dell re-installation disk and I wondered what I do to get drivers, updates etc and can I just install say XPP on it and then go to the dell site and under "support and drivers" after adding the service tag will it scan the computer and tell me what I need to install and then can I download all relevant software needed?   I'm confused as it's my 1st Dell and help would be appreciated.
No Dell install disk for XPS 420?