the only way is to contact dell.
Each Dell Inspiron has a master password which will clear the BIOS
password. You can get this number by calling Dell Technical Support at
(800)624-9896.
Dell Technical Support will request the Service Tag and Express
Service Code from the bottom of your Inspiron.
If you were not the original owner of the Inspiron, Dell will transfer
registration of the used Inspiron from the original owner with only
the Service Tag and Express Service Code from the tag on the laptop.
To transfer the registration of a used Dell Inspiron, fill out the
Transfer of Ownership form on Dell's web site.
