You can try clearing your cmos settings. This will clear all the settings in your bios. Here are two possible methods to do this:
1) you can remove the cmos battery which is the round flat battery (looks like a coin) on your motherboard. Leave it out of your computer for a few minuets and put it back in. This should clear your bios settings.
2) You can reset the cmos jumper. this will look like three pins with a plastic cap over two of the pins. To reset the cmos jumpers, simply move the plastic cap from the two pins it is on over to the next two. Should look like this:
{*[**]} -this is the jumper before the switch.
{[**]*} -this is the jumper after the switch.
think of the stars as the pins and the brackets as the plastic cap.