If you have a mother board manual, (if you dont have one, get one)
The other option is pulling the onboard battery out for about 30 minutes, this will cause the bios to go back to the default settings!
If you have a manual, you will notice on the board diagram that there are three pins. On some boards its called the CMOS RAM clear sector!
Pins 1 and 2 are normal mode and pins 2 and 3 will Clear the CMOS (BIOS)!
Most boards are shipped with with pins 2 and 3 jumpered.