|As larry has indicated the power to motherboard must be off in order to clear the CMOS. |
To verify you were successful or not check the date and time in the BIOS. If the date is correct then you didn't get the CMOS cleared. If that is the case then remove the 20/24 pin power connector from the motherboard after unplugging it. Then depress the power button a couple of times. Then remove the battery for 10 seconds and replace. Next boot enter the BIOS screens and reset the values as required.