Am I reading right that you have a Duemilanove 328 and you want to bootload a ATmega168 bare chip to make it Arduino compatible?
If so this is possible, using the ArduinoISP sketch (one of the standard example sketches in the IDE) and following the instructions here
to program the ATmega168 in a breadboard with the Arduino Duemilanove as the programmer. If it has already been set to use an external clock you'll need to have a crystal or oscillator on hand to initially bootload it, but in the process it will be set to use the internal clock so that's a one-time requirement.
According to this forum post
as your target when you burn the bootloader will set it up using the internal oscillator at 8MHz so you won't need the external clock source after it's done. I haven't tried this and that thread ends without a happy confirmation post so I'm trusting that to be the case.
Cheers ! Geoff