[SOLVED] dell xps 410 no boot

i have a dell xps 410 i recently bought it for 20 dollars so it has a intel core 2 duo and it has 360 power supply. i put a hard drive,memory,video card and dvd drive in it brand new. problem is i push the power button but nothing happens but i do get a yellow light on motherboard. when i disconnect i/o front panel connector from motherboard and short two pins on motherboards all fans start up and spin even video card fan but nothing else happens and the yellow light goes away its not power supply i put it in another computer and it works just fine same with memory video card and dvd drive. is it the i/o front panel switch for power or something else i do computer repair but never seen this one before need help

thanks