One of my coworkers was getting the following error and his machine was not booting:
"boot guard verified dxe that is fail"
After trying many different things, I tapped F10 during the boot process (the words "F12 boot options" appeared in the upper right hand corner...not sure why), but it booted to windows.
Then, once I got logged in I checked to see if the BIOS was up to date. It was not. I downloaded the latest version of the BIOS for that particular dell model and the issue seems to have been resolved.