I have a Dell Inspiron 6400 laptop with a dead internal hard drive controller. It boots perfectly from CD or USB. I therefore removed the internal hard drive and installed Ubuntu 10.10 Maverick onto an external USB hard drive. It boots and runs perfectly when doing a "cold start" of the PC. However, when I choose restart/reboot in the Ubuntu menu (e.g. after an update), I get this error message from the BIOS: "No bootable devices, strike f1 to retry boot, f2 for setup utility, press f5 to run onboard diagnostics". I can make the system boot again by pressing f2 or f5 and exiting the utility without having done anything. Or, I can simply power off the system and do a new "cold start". Does anyone know the likely reason for this problem and how to fix it. It is not a big issue but an annoyance that I would like to fix if possible.