There are 2 ways you can reset your bios.
1. On the motherboard there is a small watch battery. Remove this battery along with the power cable from the power supply. Hold down the power button to fully discharge the system. Wait 2-3 minutes then reinstall the battery and plug in your system. Your reset is now complete
2. Some motherboards have a 3 pin jumper by the battery. Lets say that the jumper is on pins 2 and 3. Remove the jumper while the machine is OFF and place onto pins 1 and 2. Power on your machine for a minute. (Note: Your system will not POST). Shutdown your machine and put the jumper back to pins 2 and
3. Your reset is now complete
There might also be an option within the BIOS to "Load Defaults" if that is all you are looking to do
please see this http://www.11a.nu/software/bios-pc-bios-security-and-maintanance-toolkit/
hope it helps!