Backdoor passwords wont work, unless a machine is specifically set up with back doors.
paradox said:
Besides, Clearing the cmos doesnt even do anything, it resets the clock, wow
If there is a password it also clear this. It could be that the person in question wants to boot from a floppy disc or CD that has been disabled in the BIOs, they could want to install a new OS so that they have admin rights, they could want to boot from a live CD so that they are able to access the network and set the proxy servers they want...
the ability to do whatever you like to a machine from before boot, (IMHO) is about as dangerous from a security point of view as benig able to do whatever you like after boot.
Anyway, to answer the question,
the CMOS is powered by a battery, you normally clear it by either moving a shunt across two short pins, (thats the technicaly name for jumpers), or by taking out the battery, (thus the Volitile RAM loses it's infomation).
Obviously, snice the RAM can be flashed etc, there is a certain amount of it that can be controlled via software, but information on this will most likely be vendor specific, and will possibly still require you to know the password.