I need serious help with my pc?

My Hp Pavilion a6532f pc all of a sudden just turned itself off while i was listening to last fm.Then i tried to turn it back on & it would not turn back on,but when i disconnected the 4pin ATX 12v connection,it then turned back on but the screen had no pic,the hard drive was not operating.The only things working were the fans,the cpu fan,the powerbox fan,& the rear fan.So would anyone know what the problem could be?