Burning Power Supply

I have a clone CPU essays main board and intel celeron 3.2Ghz, 1Gb Ram DDR2, 80GB Sata Sea gate HDD. my PC hang up & i tried restarting and in the process my Power supply burnt and i changed the faulty transistor 13005 but again it burnt when i started the PC after running for 30 second just after the beep. so am asking what could be causing the power supply to burn the transistor since my power supply is supporting other PC’s i did a test and it worked fine before i use in mine. Thank you