Compaq Presario 5451 will not boot

######### ORIGINAL PROBLEM REPORT #########

I am looking at this PC, as a favor for someone, so I don't know anything
about its history. I would like to know which hardware component is the
likely cause.

When the PC is plugged in, here is what happens:

The fan under the power connector comes on and stays on;

The green LED on the front bezel is on solid;

The lights on the NIC remain dark;

Pressing the on/off button on the front bezel has no effect, no matter how
long the button is pushed in;

HDD LED on front bezel remains dark;

No video at all;

No beeps;

No HDD activity is heard;

Also, the Compaq tape (on the back) is still in place, so the case has
probably not been opened.

When I got this PC, the switch near the power plug was set to 230, instead
of 115 as it should have been. Is this likely to have caused damage?

######### P.S. 1 #########

I have removed both cards (modem and NIC). Did not make a difference.


######### P.S. 2 #########

Well, I swapped out the power supply, bought from HP/Compaq. The only
difference now is BOTH the power LED and HDD LED on the front bezel are lit
solid green. Everything else is the same. The CPU fan is not spinning.

Replacing the PS has had some effect, but is not the complete solution.

It seems this has to be either defective motherboard or CPU. Opinions?

Would welcome any suggestions.

Thanks.

-- Jay