I've had a Google on this and it looks like there is a way to do this and several people have had success. However, there is also a fair chance of stuffing the laptop completely so I'm not going to give you that information - You'll have to find it for yourself.
The correct way is to call Dell support and get the laptop re-registered in your name. They will need the serial number and service tag, which should be marked on the machine. They will then check if the machine is on their 'stolen' list. If they are happy, they can generate a one-time password from the service tag number which you can use to access the BIOS and set your own password.
It cost cash to change ownership. (Last attempted 3-4 years ago for a cost of 85.00. ) I gave up on getting it unlocked.
boot and nuke might work if you got a floppy drive AND it is an os based lock, not a BIOS lock.
If it is a BIOS lock........ Good luck.
Seriously though ON SOME MODELS/BIOS you can jumper accross pins and do a bios reset. However be careful and fully investigate both the pros and cons of this PRIOR to performing.
as they said - is it locked in windows/other operating system, or locked on power-up (boot lock)?
Good point - What exactly happens when you power it up? At what point do you have to enter a password?
Turn off capslock on whatever computer you're on.
Get a butter knife or a flat tool.
Use knife or tool to pry caps lock key off of your keyboard.
Seriously, just ask the person who sold it to unlock it for you... or reformat it and install the operating system again.