If the recovery partition on the hard drive is no longer intact, you have no factory recovery discs, and you did not create a backup image of the hard drive, asking Dell for a set of recovery discs is your only option short of buying another copy of Windows 7.
If they can't help for whatever reason, you'll have to buy a Windows 7 Microsoft DVD complete with licence & key, install that, then download the XPS 8300 drivers from Dell's website.
You can hardly blame Dell if you never bothered to make a set of recovery discs or create a backup image.