Hello! I have used the psu calculator and at 100% usage i am rated at 387W but i have 350W psu. my pc boots fine..so now orries there but then it will say loading operating system (my mobo speaks to me) and then will show a black screen or just reboot....is this my poor barton cannot handle 2.5ghz with 11.5x and 220mhz fsb with 1.85V or my psu is undervolting? also sometimes it just reboots? hope it helps?