ArduinoISP with Atmega8

Hi

I´ve got a problem with ArduinoISP. I tried to burn the arduino Bootloader on an Atmega8 microcontroller with an Arduino Duemilanove. I do everything described in the tutorial, but I always get this error:

avrdude: Yikes! Invalid device signature.
Double check connections and try again, or use -F to override
this check.

The Atmega8 has already another Bootloader, may this could make problems? And, what means "use -F"? Where should I type it? :-?

Maybe somebody has a solution to solve my problem.

Christian93

Dont forget to set baud rate.

-b 19200