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I've got a dual-monitor setup using a GeForce 7900GT that was working fine for over a year... then suddenly, only one of the screens works.

It's not OS-related, because even on startup, only one screen displays the BIOS checks. In the past, both screens would show it together.

  • I didn't change anything to trigger this
  • The monitor that gets a signal is random -- sometimes the one on the left goes black, sometimes the one on the right.
  • The monitors and their cables are good -- I can switch both or either, and I get a signal just fine. They're plugged in, too.
  • It's not the video card, either -- I have an identical 7900GT in another machine, and swapping the two didn't fix anything.
  • It's not dust on the motherboard -- I pulled everything out, cleaned it off, checked for obvious damage, put it all back together, and no change.

My next two steps are going to be to reset the CMOS info and to try swapping out the motherboard.

Before I do that, does anyone have any other ideas?

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"swapping the two didn't fix anything" I assume you mean the problem stayed with the machine and didn't travel with the card. Good luck with the CMOS, but your motherboard or your power supply is in need of replacement. It's easier to test the power supply. If desperate, feed the back-side of the 7900 with the other machine's power cable; this will either confirm the power problem or leave you with two broken machines. – msw Jun 10 '10 at 3:58

You've ruled out the video card being the problem, so it must lie in either the monitors, power supply to the whole lot (you aren't draining too much power for both monitors to run are you?) or the computer itself.

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