I've got a MacBook that won't boot beyond the grey screen and chime. (So I see the grey screen and I hear the chime) After this all it does is a rapid cycle display of the apple logo, and a No-entry type sign, and a Question mark. All of this on the grey background.

I've tried clearing PRAM, etc, but no joy.

There is no problem with the hardware as I can boot from an Ubuntu Live CD with no issues and that runs quite happily.

This problem occurred immediately after installing the software for a ZTE Modem. So what I want to do is go in with Ubuntu and remove the offending files from start-up. What I am finding though is that Ubuntu can read the HDD but can't delete files - so how do I delete files using the Ubuntu live CD, please?