Desktop stuck in short boot loop

XPS 420, Bios - A07, Windows 7 (installed about 2 weeks)

I woke to find my desktop in a boot loop.  The "Dell" screen displays, the bar fills, then it goes back to the generic start screen, then to the "Dell" page, and repeats forever.

I did a restore from my Carbonite mirror and it seemed to work but it still does the loop/boot cycle.

I need a diagnostic disk to tools to test and verify the system.  Any way to download software?

Ed