|If you have a floppy disk inserted in a floppy drive while booting the computer, if the floppy disk IS NOT bootable (does not have an operating system installed on it) , you will get a message similar to the one you got and the bios will NOT try to boot the computer from anything else - the boot process will halt. |
If that's your problem, eject any non-bootable floppy disk in a floppy drive BEFORE booting the computer
If you have an older Dell computer, some Dell bios versions are set by default to indicate to the bios that you have a floppy drive installed. If you don't actually have a floppy drive connected, you get a FALSE message like you're getting and the boot process halts. You must go into the bios and change that default setting to tell the bios you DO NOT have a floppy drive connected, Save bios settings.
If you have a USB flash drive plugged while booting the computer, USB flash drives are NOT bootable unless you prepare data on them to make it bootable, and depending on bios settings regarding what devices the computer can boot from, you MAY get a message similar to what you're getting and the boot sequence will halt (when the bios attempts to boot the computer from a USB connected drive).
If that's your problem, unplugging all USB flash drives before booting the computer should cure your problem.