How to Reset BIOS Manually
The computer BIOS is the basic input output system that tells a computer how to use the hardware; the computer won't run without it. The BIOS is editable by users, but sometimes a mistake can make it impossible to go back in and correct it without manually resetting the BIOS. This is easily done and the defaults will be loaded back into the BIOS.
Things You'll Need
Turn off the computer. Open up the computer case by unscrewing the case access door from the back of the case. You may need to push a button or release to have the door open as well.
Read the computer manual to find where the BIOS reset jumper is located on the motherboard. It is usually near the CMOS battery, which is about the size and shape of a nickel. Pull the jumper out.
Start the computer and after a few seconds turn it off again. Put the CMOS jumper back in place. Close the computer case and start the computer again. The BIOS should now be reset.