System\admin password

Hello,
When I turn on this Dell Inspiron 1545, service tag number 24NL9H1 Model No. PP41L, all I see is "This computer system, #24NL9H1-595B, is protected by a password authentication system. You cannot access the data on this computer without the correct password.

Please type in the system or administrator password and press enter."

I've tried F6, F8, F12, CNTRL ALT SHIFT, CNTRL ESC, and a few others. Nothing happens. I press ESC and it shuts off. How do I get around this? Any help would be appreciated.