The only way to disable it is to call Dell (there is a charge if you're out of warranty), verify ownership, and they'll issue a system-specific bypass for you.
The only way to reset the BIOS password is giving a call to dell technical support department, you will need to provide the service tag / express service code and you need to verify the ownership of the equipment, what is the name of the original owner (name on the dell order) the original address where the equipment was sent. thats the only way to do it, there is no jumper on the motherboard or any other class of procedure to clear the BIOS security.
Kevin O Pereira
Technical Support Analyst
DCSE Certified | ESF1 | GTS
Ex-Dell El Salvador Employee