I've read everything I can find on this - thanks to everyone on this site for posting such useful info - but I have not gotten it sorted yet. Here's the deal: Early 2005 G5 Tower, 2.0 ghz DP - left unplugged for a few months. Will not boot. No chime. No flashing light (light is steady when "on") Will not progress past the gray Apple screen. Left on, the fans go crazy after five minutes and I power it down. It will not safe boot, will not boot from commercial Leopard disk, will not boot from original disk (disk1) .... BUT will boot from Apple Hardware Test (disk 2). Hardware Test finds no problems. I replaced the battery. Reset PMU button (pressed only once, waiting 10 sec) still won't boot. RAM is good, tested on another machine using rember. Will boot in Open Firmware, but I don't know what to do with this.... If I leave open firmware open for 15 minutes, it freezes up and I have to power down. Reading this helpful forum makes me think it might be the logic board, even though it passed Apple Hardware Test. Any suggestions you guys can make? Thanks in advance. J.