Hi to all... im having a little problem today when i got in i turned my computer on but all i got was a big bang . so i cut the power off and opened my computer. i could not smell any burning, so i changed the psu with an old one i have which is 300 watt where as the other one was 650 watt it then powered up and come on but when it gets to the xp loading it just shuts off could any one here help me diagnose this problem..... Thanks I think my other power supply unit has blown for some reason. because when i use that i get no power.