I have a new XPS 8910,  I accidentally deleted the USB option from the list of boot options in BIOS.  In fact, it seems like I can only boot from the C: drive.  

THis is a problem because I want to do a fresh reinstall of Windows 10.  After a recent Windows 10 update, I lost access to Windows store and can nolonger run any Windows apps.  All of the apps disappeared from the menu. I tried the WSReset and other fixes offered online without sucess.

How can I repair the damage I did to the XPS 8910 boot option list and add the USB option back?