We recently had a computer come into the shop (a Dell Inspiron 1420) with a locked BIOS password. The user had no idea what it was. Normally, we buy the passwords on eBay or use password crackers, but we thought we’d try a great online tool at http://bios-pw.org/. It worked for the admin password no problem.
When the password prompt comes up, enter the wrong password, and then you’ll see your service tag or system info. Plug that into the website and try the passwords it gives you, the second one worked for us. If that doesn’t work, you can always buy one on ebay. Just search for “computer model BIOS password”.