If you've turned off the BIOS function completely then the easiest thing to do would be to reset your CMOS completely.
Open up your computer and look for the round silver battery on the motherboard. Gently take the battery out and wait for about 10 minutes before putting it back in. This will reset all your BIOS/ CMOS settings back to default and you should once again see the prompt page at boot.
Picture of what the battery looks like: