i've had a couple of A-bit motherboards with the same problem. either after adding a new card, or sometimes at random, the pc won't start up again, and on pressing the power-on, the power led flickers momentarily and then nothing happens. i then have to clear the bios, and sometimes the pc will start again, but other times i have to do this a few times before the pc starts again.

What models are they?

NF7-S and KD7-G

I take it you have been using different power supplies to remove that from the equation?
Most of my motherboards have been abits and I've been hit with this problem also. Got an rma for a st6 raid board that would do the same and decided to replicate the fault on the bench b4 I sent it off and guess what its still working ok.

nal

initially i thought it might be a power supply problem as i was using only a 300w, but have put in a 550w one and still have the same problem

Originally posted by ellal
initially i thought it might be a power supply problem as i was using only a 300w, but have put in a 550w one and still have the same problem

550!!! You running the FBI mainframe???

Ahem, i have a dim and distant memory of my first Abit board which would only POST once every four or five attempts if there was a problem with the BIOS settings. I sent the thing back, got a new one and had the same problem - i was very embarrassed when i read the manual and found it was supposed to do that ....

So, anecdote done, is all well with your BIOS? And all your cards and leads etc are properly seated, no shorting of the board etc ?

Maybe that problem is occuring because you can't say/spell that name of it, lol...its abit...

Anyways, have you attepted to clear the CMOS?

I have an NF7s and no problems of that sort. There is a 12v power connector as well as the main atx power connector. Make sure both are plugged in as the nf7s is power hungry, so the 12v supply keeps the 12v rail stable, unsurprisingly.

Also try updating the bios to the a recent version and see if it helps.

I have to agree it sounds more like a power supply issue than a motherbaord problem. Check that the motherboard isnt shorting out on the case and all screws fit flushly.

hey, copyright...i may not be able to spell but i can read (see first post)...lol

tried plugging in the 12v supply, but still the same.
Can't update the bios (if there is a newer one), as i can't get the pc started!

have tried booting with only the graphics card connected, and have tried out new cpu, memory etc.

If the mobo was dead I would expect to hear no whizzing fans no drives spinning up or anything.

Is the power light on the mobo? Its a red one on the bottom towards the front of the case. If not then send the board back is the only option i think.

are you running xp?

power light on mobo is on. starting up causes power led on case to flicker on/off