BIOS password reset on Dimension 2400

A password has been set on my BIOS.  I can't boot up the system at all.  I've tried some possible default passwords, or my own personal common passwords, but nothing is accepted.  I think there may be junk in the password because I did not intentionally set it.  It is usually left on all the time, but came in one morning and it was off.  When I turned it on I get the to Enter Password prompt.

 

PLEASE HELP.