Hardware Failure Advice

Tried both HDDs individually, as you suggested: no change.
Tried each memory stick (2 identical) individually: no change.
Tried resetting CMOS: no change.

I'm tending to think the MB is at fault: what do you think?

lhutton,

Have you tried replacing the CMOS battery as it may be dead? Can you hear/see your CPU fan working?

All fans are working. Would the CMOS battery be likely to die after less than a year? (I've had MB for 11 months).

When I've seen a CMOS battery die, I've still been able use the computer. In this case, I can't get anything on the screen.

Are your hdds western digital ?
If so -  changing master / slave jumper settings on your hdd when trying to boot from a single hdd - remember that there is additional setting besides <master/slave>  - it's <single drive> setting (no jumpers)

Are your hdds in a stripe /raid mode?

Check for unusual noises/ power up noise from your hdd.
If the hdds are ok, - check the IDE cable ribbons.
It's possible your onboard Ide controller is gone - if motherboard replacement is out of question  you can get external PCI IDE controller such as the one from Promise or SIIG.  
Are we getting closer?

Seems as if i missed your last comment - power up your computer as usuall, check for motherboard post sounds (BIP) - many of them signal problems this way.
Press numlock button on your keyboard, does it light up/down ?
If so, the problem could be graphic card or monitor

Both are Maxtor. Have tried with no jumpers, as Ultimate_NescaFe suggested.

Not in stripe / raid mode.

No unusual noises. Cable ribbons look fine.

No MB post sounds. No keyboard access.

Graphics card fan still works and monitor still works; just nothing showing. The giveaway is with the disk light being permanently on, so looks like it has to be MB.

Will do, thanks. Fortunately, MB is still (just) under warranty.

Is the Power Supply fan turning?
Do you have another PSU to test with?

All fans are working.

the fans running do not mean you are getting voltage on the motherboard. Grab a P/S and hook it up and test. I would alomost bet it is the P/S. chedap and eaiser to test the P/S before you pull you system apart.

try another video card, even a cheap pci one will do

lhutton,

When you tried each memory stick independantly, I assume you transplanted them to the correct slot.... I'm betting the power supply is bad and supplying incorrect voltages to the MB as suggested above.

I've never had a mother board just die out of no where..... MBs usually get a little flakey before giving out, at least that is my experiance.

Just because all fans are running means nothing too me. If my memory serves me correctly, on ATX boards the HD is twelve volt, the PCI, ISA,  cpu Heat sink fan (and all other fans) and the floppy drive are all 5 volt, and the processor and memory is 3.3 volts.

It is my opinion that the 3.3 volt lead from your power supply went out. Thus causing your processor not to execute its BIOS instructions. Even if the MB was bad, I see a 1 out of 5 chance it would prevent you from atleast seeing the bios splash screen.

I don't know who this guy is that keeps harping on the cmos battery in every question for the last week, but the system would still load with a bad battery. you would just lose some settings and your system time would reset on every boot up.

Mugman

One more thing, sometimes power supplies go out like light bulbs, they just suddenly pop and become worthless. MBs and other expansion cards pratically never do this...... after thinking about this for several more seconds, i'm will to bet just about anything it's the 3.3 v lead on the power supply. I'm sure of it!!!!!

Mugman

Mugman spoke !

Is there any way, perhaps using some device, I can check whether the P/S is at fault?

With a VU meter. The do-it-yourself technician always carries it (as do the pro's).
You can get one cheap at your local DIY shop.

I'd think you can check if there is -any- curerncy by hooking up some LEDs to the right pins, but you really need some accurate ratings...

Maybe a handy neighbour?

There is also a ATX power supply tester you can get from a computer shop or electronics store. It plugs into the 20 pin connector. Might be worth looking into.

Antec Power Supply tester. $15.00 it can be found at Antec.com

I don't see the need for you to buy a $15 tester when power supplies usually cost only $30. If you took your power supply out, and went to your local electronics store, they would probably test it for free.

Stores like circut city, fry's, best buy, ect have repair techs working there usually and would have a tester avaliable, if they try to charge you, take your business elsewhere or complain to management and be persistant.

Mugman

Managed to source another PSU to try and no change.

So, looks as though the problem must be with either the CPU or MB, having disconnected all unnecessary cards and CD-ROMs and played with the HDDs, FDD and RAM.

Seems like you've pretty much narrowed it down to the motherboard, since more chance of a bad mobo than cpu and a bad cpu would probably not light up the HD Led.

Rob

I never tried holding the power button in; always had to turn off at back.

Yes, I removed everything. Am right now having system checked by someone more in the know than me before having MB sent back.

Thank you for your help here. Will let you all know how I get on...

Well, it turns out it was the motherboard! I have everything running as normal again :) Thank you all again for the valuable help and suggestions: definitely appreciated!