If using a Dell-branded Windows 7 DVD, your Product Key on the sticker should work just fine to activate (if it asks you for it at all).  If you use the ISO to create a DVD from the site I mentioned, activation with that Key will fail, but you must still enter it to get a code to supply Microsoft when you call.  You can, however, activate by phone using that key and the generated code you get when you click on "Activate by Phone".
Hello there, I was wondering whether it would be possible to use a Windows 7 disk to reformat my computer, as opposed to the Recovery disk given. I had been infected with a virus that would not allow my computer to boot and the recovery partition on my hard drive had been corrupted. Would it be possible to use a standard Windows 7 disk, I do have the Driver's and Programs disk that came with the computer. Would that work. -Thank you for your time, Jtieu1991
Dell XPS 7100. Clean reformat