Answer to: sometimes won't bootUnplug the power - from socket, then from PM G5. Removal door and plastic fan shield/guide. ground yourself and ensure you & PM are not on the same carpet - preferable non at all. Remove the CPU/RAM fan. under the bottom bank of RAM there is a tiny silver button, press it, re-install everything previously removed. Power on unit(on Last 2005 PM they have no PMU ... this function is the SMU which I gave to reset.