If you don't use a crystal or ceramic resonator on your atmel mcu, then the clock frequency will very probably not be accurate enough for the bootloader to work even if you do manage to burn it. However, you can still use ArduinoISP to upload your sketch directly, without a bootloader. See Prototyping small embedded projects with Arduino | David Crocker's Solutions blog for how I used to do it before I purchased an AVRISPmkII.