My mums pc died one night almost 2 weeks ago.  The PC is Athlon 64 socket 754 - MSI NF3 motherboard - decent psu - 1GB geil ddr 3200 ram - ati 9800xt.

On first switch on of power on back of psu the fans would spin up for a fraction of a second and then stop.  Then it would be unresponsive to the power button.  So I unplugged the 4pin 12V connector and pressed power and fans span up but no display.  

I suspected a PSU problem so I swapped it for one of my spare 300W PSUs.  Same result.  I then tried each component in an old Athlon XP 1600+ system.  Memory + gfx card worked ok so I know nothing is wrong with either of those.  I suspect its probably the MSI motherboard so I get a replacement from Ebay.  Thats another story which I wont go into.  

I setup the pc with bare minimum (new MB + CPU + Memory + GFX card) with the new PSU and get same result - fans spin up but no display.  This leads me to getting a CPU.  I picked it up from the Post Office today and expected the system to work...  Of course it hasnt, its doing exactly the same thing.  I have also now got some RAM from a friend and it does exactly the same with that.  I have tried different GFX cards (Matrox G400 + ATI 9500) and no dice.

Any suggestions as to what the hell is wrong with this PC?  There are no POST beeps which would give indication as to the fault.  Is there anything I havent tried other than binning the lot?

Tried with CPU only?

Motherboard sounds stuffed to me though.

Tried 2 different motehrboards exactly same results.

Oh, and new PSU was tried on the Athlon XP system and worked ok.  Old PSU is definitely dead. :-/

does it work on a bench? sounds like a short to me.

Quote from: Eggtasticodoes it work on a bench? sounds like a short to me.

I was going to say that the only thing your left with is the case. Like Edd says - try is out of the case or in another case (if you have one).

And I just got the old motherboard + old memory + old cpu + ati 9500 to boot....
*sigh*

Im going to rip out the new Motherboard and try it on bench like you suggest to see if it is a short.  Otherwise the "new" motherboard is going back as faulty.  I am already in dispute with the seller so this is going to be fun if it is faulty.

Benching it would be my first step.

Then just fire up the board solo, no memory nothing just to see if fans spin.  If it beeps then your getting somewhere.
Then add each item solo and check for beeps.

I havent had any beeps no matter what I have done in my tests.  I am about to get around to trying it without the case.

Well, it seems the "new" motherboard is definitely DOA.  The old motherboard which I thought was dead is now alive again and I have confirmed both CPUs, memory, gfx cards work in it.
This has been an exasperating experience that has cost me a new PSU, a new CPU and a "new" motherboard.  At least I will be getting a refund for the faulty motherboard.