How to reset bios password on dell latitude e6400

The above answer is not totally correct. Any solution regarding removal of battery, shorting pins together, etc does not work. However, what does work is to use the Dell Asset/Service Tag BIOS Reset Tool. Find an Bootable CD ISO of the tool (can be found on torrent sites or email me and I can send), boot the CD image and when you are asked if you want to delete/change the service tag select "Y". When asked for the new service tag number re-enter your current service tag. Then the tools erases the BIOS and inputs the new service tag. A by-product of this process is that the BIOS master password is removed from the BIOS.I knowthis works because I just did it less than one week ago.

That cannot be acomplished unless you know the code. If you have electronics or computers knowledge, remove back cover, remove BIOS battery, wait a few minutes, put it on place, place back cover on, and power up notebook. There is no password.

This information is intended for experienced users. It is not intended for basic users, hackers, or computer thieves. Please do not try any of following procedures if you are not familiar with computer hardware. I'll not be responsible for the use or misuse of this information, including personal injury, loss of data or hardware damage. So use it at your own risk.
A. By Using the Motherboard Jumper:
In most motherboards CMOS battery is soldered, which makes it difficult to remove the battery. In this case we use another method.
Almost all motherboards contain a jumper that can clear all CMOS settings along with the BIOS password. The location of this jumper varies depending upon the motherboard brand. You should read your motherboard manual to check its location. If you don't have the manual then look for the jumpers near the CMOS battery. Most of the manufacturer label the jumper as CLR, CLEAR, CLEAR CMOS, etc.
When you find the jumper, look carefully. There will be 3 pins and the jumper will be joining the center pin to either left or right pin. What you need to do, is remove the jumper and join the center pin to the opposite pin. e.g. if the jumper joins center pin to left pin, then remove it and join center pin to right pin. Now wait for a few seconds and then again remove the jumper and join the center pin to left pin.
Make sure to turn the PC off before opening the cabinet and resetting the jumper.

B. By Using Software:

I have found that BIOS/CMOS Password Recovery Tool is the most effective.:
BIOS/CMOS Password Recovery Tool is a program that works instantly to remove any lost or forgotten BIOS/CMOS password. Simply boot your PC to DOS and execute the program, and get access to forgotten BIOS/CMOS passwords in just seconds
BIOS/CMOS Password Recovery Tool Service: http://www.biospasswordrecovery.com/