The easiest way is to just reset to factory default, if your laptop includes a CMOS battery that is accessible then you could take it out and wait 10 seconds and put it back in that normally clears the cmos
http://www.ehow.com/how_4740583_reset-bios-laptop.html
When you first turn your computer on,
you are briefly presented with a BIOS
"splash" screen. Somewhere on this
screen (just where depends on the
manufacturer), are instructions on how
to access BIOS settings. Generally,
this requires tapping a function key,
say F2, while the splash screen is
visible. Make note of which key the
splash screen says to press to access
the BIOS and restart your computer.
When the computer boots and the splash
screen appears, tap the required
function key quickly to enter the BIOS
settings screen. You will only have a
couple of seconds to hit the right key
and if you miss it you'll have to
restart the computer and try it again.
Once you successfully enter the BIOS
settings screen, use the arrow and
function keys to navigate the menus.
Keep an eye out for an option that
says something akin to "reset to
factory defaults." If you see this,
follow the on-screen instructions to
reset the BIOS to the factory
settings. Then, confirm your choice
and exit the BIOS screen, usually by
pressing escape. Congratulations, you
are done.
If your BIOS does not have an option
to return to factory settings, things
are more difficult. Because the BIOS
is stored in ROM, it must have a
constant power supply to store any
changes you make to it, otherwise it
would reset every time you
disconnected your laptop from AC
power. Removing power to the BIOS
resets it to factory settings and
involves disconnecting a small battery
attached to the motherboard. On many
laptops, the BIOS battery is easily
accessible through a door on the
bottom of the unit. Unplug the
computer, remove the main battery and
touch something metal to ground
yourself.
Remove any screws holding the BIOS
battery door in place. Then identify
the battery, (it is generally a small
lithium "watch" battery), and remove
it taking care not to damage any
surrounding circuitry. Let the
computer rest for a minute or two to
discharge any remaining power, and
replace the battery.
If your laptop does not have an easily
accessible door for the BIOS battery,
you may have to dive deeper and
disassemble the computer to find it.
Consult your laptop manufacturer's
website for information on replacing
or removing the BIOS battery from your
laptop
