You can boot from the Dell DVD or USB, select troubleshoot, and then 'reset my PC.' Reset my PC gives you the options to preserve your data files (but not applications) or wipe everything.
Unlike with Win 7 media from Dell, or a Windows 10 DVD from Microsoft, the Dell recovery only gives you a repair option, not a clean install option.
(You can also download the ISO from Dell as well as as tool to create a Win 10 Recover bootable USB key.) with downgrade rights.) Dell will provide a Windows 10 Pro recovery DVD. My company has purchased several desktops and laptops from Dell with Windows 10 Pro licensed but Windows 7 Pro installed by Dell (i.e.
