Before decreasing my reputation please let me know what I have done wrong. Bear with me as I am a newbie.

I have 2 microcontrollers (Atmega 168PA-PU). So far I have run the following program in one of them (say mc1). Now when I run the same code in the other one it gives erroneous results. Someone suggested that the inbuilt RC oscillators give +/- 10% error in system frequency and that is enough to throw the device out of balance. So I have decided to use external 12MHz oscillator crystal and connect them to XTAL1 (pin 9) and XTAL2(pin 10) with 22pF capacitors (ceramic). I burn my programs with avrdude. So please can anyone help me with the appropriate fuse setting I should use. The AVR fuse calculator confused me even further.

Please help !!! If you need any details let me know.

I have 2 microcontrollers (Atmega 168PA-PU). So far I have run the following program in one of them (say mc1). Now when I run the same code in the other one it gives erroneous results. Someone suggested that the inbuilt RC oscillators give +/- 10% error in system frequency and that is enough to throw the device out of balance. So I have decided to use external 12MHz oscillator crystal and connect them to XTAL1 (pin 9) and XTAL2(pin 10) with 22pF capacitors (ceramic). I burn my programs with avrdude. What is the appropriate fuse setting I should use? The AVR fuse calculator confused me even further.