Checked and updated to latest bios. No boot disk in drive.

Perhaps I should explain why I want to be able to do this. Weekly, I back up my system to an external hard drive. I use Aomei Backupper, which uses a rescue cd, to access the external hard drive, when needed. I have needed to do this several times in the past few years on my previous computers, and I want to be able to do this on this new Dell system, but I'm unable to do so, if I'm unable to boot from cd.