Problem burning bootloader on ATmega328P using internal clock
If your ATMEGA328P has already been used with a crystal or already has a bootloader on it, then the fuses will be set to expect a crystal oscillator. In this case, you must initially have a crystal &amp; the associated 2 capacitors connected. Once you have succeeded in burning the bootloader (this process also sets the fuses) you can dispense with the crystal.