P4I865PE Dragon motherboard with P4 2.2GHz on WinXP

Recently the computer would just not start about being shutdown from the
front switch. The only way to restart would be power it off from behind,
wait 5 sec and then power it on. Doing so, the fan will start then halt for
a moment and then finally start. I've ruled out the power supply by using a
new power supply. The front switch is also okay (I have the switch
configured to present the ShutDown/Suspend/Logoff option and that's what I
get when I press the switch).

There is a small LED next to the CPU, on my other P4 machine this would
always remain lighted even if the computer was shut down. But with the
troubled computer this light goes off once the computer is shutdown. ATX
supplies are supposed to have a trickle voltage and I believe the LED is
driven from that trickle charge and could something be just eating up the
trickle charge. Or could something be causing the PSU to not produce this
trickle charge ?