In BIOS setup, boot option is disabled issue

[sanjivani.d22]

I am unable to login in machine as windows 8.1 got corrupted. So was trying to update the system from USB drive, but it is not shown in boot options.
Now when I want to add one, the boot option is disabled and greyed out. No action is performed on Enter or arrow keys in Bios setup.

BIOS version: A10
Product: dell Inspiron 5520

The help is really appreciated.
Thanks

 

[norcalsc]

Try a different usb drive. Sometimes they are junk