I have 2006 Mac Pro desktop that will not boot after PRAM reset. Symptoms started this week with Apple Trackpad going bonkers. No multi-touch gestures. Barely right click. Sometimes cursor jumped all over screen. I thought it was the batteries in the trackpad, it wasn't. Thought the trackpad was going bad... possible, but doubtful. Plugged in a wired magic mouse and tried resetting PRAMs since I read that might fix the trackpad problem. After PRAM reset... no reboot. Not in recovery mode, target disk mode, safe mode, verbose mode. Tried them all. I am running a 06 MP hacked with Yosemite, but it has worked flawlessly for months. Possible logic board issue? I was reading about the logic board battery. It is 8 years old after all. Any thoughts to force a reboot? thanks.