At this point, no hardware issue is indicated, which is consistent with the error. What you're getting is a TDR error, which are not uncommon for AMD cards (one reason I avoid them).
Have you already worked through the solutions in this article? Since your problem occurred right out of the box, I don't think it's an overheating issue, so I would look at solutions that involve updating the system BIOS, updating DirectX, etc.
If things don't improve, the next thing to do is back up your files and restore the Dell OS. That will restore the original driver that shipped with the system, which you will then need to update, so have the current AMD driver handy.