Missing Dell BIOS (boot) password

I have a client's machine on which one of his darling little brats has created or reset the BIOS password and now denies all knowledge of the thing. I seem to recall there is either a means of generating the default password from the Service Tag or, failing that, shorting out one of the motherboard chips. That I have done before but would prefer to know which chip it is.
The system is a Dell Dimension 3100.
Anyone able to help before I condemn the thing to perdition and a drop kick into the neighbours wheelie bin?

Sorry I don't know all that much about this, but could you try resetting the CMOS via the jumper on the board or removing the battery??

Maybe this will help? http://www.tech-faq.com/dell-bios-password.shtml