Hi,

When I unplug the AUX power, I get System Fail CPU Test....

When I plug it in, I get nothing- no power up, nothing.

I have a ASUS P5AD2 Deluxe and an Intel Prescott 3.0

Any ideas? Mobo shot? CPU shot?

thx all.

Did the system ever work ok?

Yes, it worked fine for two days... then kaput. Also of note, when I took the MB out and the CPU off, I noticed the material that used to be on the heat sink has sort of melted off and is now on the processor.... hmm

I noticed I wrote "AUX power"... I meant the four-pin ATX 12V power connector. I also have a new power supply with the req'd ATX 24 pin plug.

It's normal for the thermal pad material that came with the CPU heatsink to soften and get on the CPU die.
But whenever the CPU heatsink is removed, then the thermal material should be wiped off(use a credit card to remove the bulk of it, and remove the remainder with a soft cloth and 91% pure or higher alcohol) from both the heatsink and the CPU die, and replaced with thermal compound. Arctic Silver is recommended, but you can also use compound available at Radio Shack in a pinch.
And make sure that no thermal compound gets on the CPU board.
Finally, make sure that the CPU die is not chipped or cracked.

When you say 'you also have a new power supply', do you mean one that's not currently installed?

No, it is the one that's currently installed...

After applying new thermal compound, and determining that the CPU is ok, then do the following:

Try a different monitor, or connect yours to a different system.
If there's a display on another monitor, or if there's no display on yours, then replace your monitor.

If the monitor is ok, then install/connect only the power supply, MB, CPU, memory, video card, monitor, case speaker, and power button, and make sure the power supply's voltage selector switch is set to the correct voltage and the PS connection to the MB is securely seated.

If there's no display, then clear CMOS with a MB jumper, or by removing the CMOS battery for at least 30 minutes.
If no luck, then make sure the 'Clear CMOS' MB jumper is not in the 'Clear' position.
If the jumper is in the proper position, then check the CMOS battery for the correct voltage(3V).

If no luck, then check the MB capacitors for any leaking, bulging, or rupturing.

If they're ok, then place the MB on a piece of cardboard. If there's now a display, then the MB is shorting out when installed in the case. Check for a loose screw, standoff, etc., inside the case, and also remove any standoffs which do not line up with MB holes. If none is found, then remove all MB screws and metal standoffs, and install paper washers(manila folder paper works good for this) between the MB and the screws/standoffs.

If there's no display with the MB placed on a piece of cardboard, then proceed with the following:

(1)If the MB standby LED does not light up when you turn on the power supply's switch, then check the wall outlet, surge arrestor, and power cord for the correct voltage.

(2)If the voltages are ok for the items in (1) and the MB standby LED still does not light up, then then slightly raise the PS main power connector out of the MB connector a little. If the MB LED lights up, then the connector on either the PS or the MB is bad. If the MB light still does not come on, then the PS or MB is bad. Swap these 2 items out to find which one is bad.

(3)If MB light comes on, but the PS fan, other fans, and other lights do not work when the 'Power On' button is pushed, then make sure the computer case power button's wires are securely connected to the correct MB terminal(POW-ON, Power On, etc.), and that the wires are not shorting out(bare spots). If that's ok, then remove the power button's wires from the terminal, and momentarily short out the MB terminals with a screwdriver. If the fans and lights now work, then the 'Power On' button assembly is bad.

(4)If the fans connected to the MB and all other lights do not work when either the 'Power On' button is pushed or the MB 'Power On' terminals are shorted, then the MB or PS is bad. Swap them out.

(5)If all fans and lights work when the 'Power On' button is pushed but there's no display, then test the following PS leads on the back of its MB connector making sure the connector is installed on the MB and system is powered up with the 'Power On' button:
yellow wire and a black wire- +12V
red " " " " - +5V
orange " " " " - +3.3V
If these voltages are not up to spec, then the PS is bad.
If you do not have a voltmeter, then try a different PS.

(6)If the PS voltages are ok, or there's no display with a different PS, then either the MB, CPU, memory, or video card may be bad. Make sure the correct memory type is being used, remove and reinsert the memory a few times making sure it's firmly seated, install the memory in different slots(some MB's require that their memory slots be populated starting with slot 4 and not slot 1), and make sure the video card is firmly seated(some video cards need an extra firm push to seat properly). If still no display, then swap out the MB, CPU, memory, and video card to find out which one is defective.