My g5 1.6ghz tower will no longer boot. I get the chime on starting up and white screen but then it just turns off. I had being trying to reinstall os10.5 as I was having problems with some drivers. My current os was 10.5.6. It refused to reinstall and after trying to restart, this happens. I have tried resetting the smu. Still the same. Any help or advice would be gratefully appreciated.