monitor no signal, casing lights fails.

i was having a problem with my computer, i thought it was the motherboard problem or the processor thus i replaced them.

After that ,with the new hardwares, the monitor no signal, mouse no power keyboard no respond, but the cpu fan, graphic card fan are working.

plus the lights on the casing that are suppose to flash at the start is dead. the casing light the the 'on' button is dead also.....

i tried popping up rams graphic card checked all connections, there seems to be nothing wrong.

so i thought maybe it is the power supply 's probem. after posting at the
PSU section i was suggested to change my PSU, and i did, but it doesnt seem to work...

so im thinking if it is the motherboard and cpu problem ?
i really need help on this...

spec:
mother board:G31M3-f
ram:2x 512mb kinston
graphic card: ATI1600pro 256
harddisk:120gb

new power suply: cooler master, 460w