dual screen not working after power outage

Hello, after a power outage two exactly same computers had the same problem. it is two HP 7800 and both have an Nvidia 8400 GS with two screens each. the video card is pci x1 and has a unique port attached to a cable that outputs two vga ports which are connected to the screens but since the outage only one screen works. both computers have the same issue so i checked the screens and they work fine, i checked the card on another computer and it worked fine. i'm not sure what to do next. could you help me? is it possible that the pci slot is not working anymore or there's not enough power for 2 screens or some settings have been messed in the power outage, i don't know what to try...

thanks for reading! double thanks for your help =D
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More about dual screen working power outage
  1. Seems trivial, but did you verify under your display properties that the second monitor is enabled by checking "Extend my windows desktop onto this monitor?"

    Also, if the monitors are plugged into a power strip, try hitting the reset button if there is one.
  2. oddly the second monitor is enabled and i can move the mouse out of the primary screen but the secondary screen is still in "sleep mode" as if it was detected but couldn't receive the image. i switched cables in every possible ways also tryed to reset both computer and monitors (cut the power to it) and i came to the conclusion that nothing is coming out of the second vga output BUT if i plug something in or out of this secondary output, the primary screen flickers as if it was acting to it. i'm starting to believe it could be software issue... somehow i have to reset something somewhere....
  3. Try attaching 1 monitor to the "bad" port and boot the workstation. Do you see anything on the screen at any point?
  4. I tried that and it turns out that there is no bad port. Both ports will work and the second monitor is detected because I can see dualview and clone options on the display properties as well as I can change the resolution for both screens but there is no image on the second screen. The card works great on another computer and it's hard to believe that there's a hardware issue otherwise it would be a very pervert one !

    I might add that on the nvidia taskbar options list it says (analogic) next to the first screen and (numeric) next to the second but both are DVI(screen) to VGA(card).

    I tryed using another PCIE bus and i had to reinstall the drivers but it was still not functionning...
  5. This is a VERY late reply to this issue, but it might help someone. I had a similar problem whereby my extended screen would not activate, despite its being perfectly OK. I solved the problem, although I don't understand why it worked. It was caused by two Users (both with Administrative privileges) having different power settings, only one of which was a STANDBY after 20 minutes. By setting all users with identical power settings, the screen came back to life. As to why a smaller (temporary) replacement screen did not exhibit the same issue, I can only guess that it was because it required setting to a much lower resolution, which must have somehow ignored the power setting. Anyway, I wanted to record this somewhere in case someone else has the problem.
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