Complete desktop reinstall

[arizonaf1]

So when I turn on my dell all in one xps desktop computer it says reboot and select proper boot device or insert boot media in selected boot device and press a key. When I press keys on my keyboard nothing happens. I don't actually want to do a reboot or back anything up as I am trying to completely wipe it clean and restore it to factory settings before I sell it. I just need to know how to bypass this and restore it to factory settings. Please help!!!

 

[Emerald]

check the BIOS and see if the HDD is listed.