dual monitors

Bought a video card for an HP desktop so I can run 2 monitors.  On the desktop there is a vide card that has a vga port and a dvi port.  I tried at first to plug in 2 monitors to this video card but only 1 ever shows up.  Can this be done?  So, on to the purchased card.  I plugged it in and it has a dvi port on it plus an adapter for vga.  First I plugged in vga to the current video card and used vga port on the new installed video card.  When I reboot the new video card works fine but it must be overriding the other video card that came with the computer because only 1 monitor works, the one that I just plugged in.  So I tried going directly into the dvi port of the new card and the dvi port of the existing card and the same thing happens, only the new card monitor will come on. Any ideas of where to start?
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Tim PhillipsWindows Systems AdministratorCommented:
You only need one video card if it has two ports on it.  Are you telling Windows what to do with the video outputs?  (ie extending or cloning the screens)  

Follow this if not:  https://support.microsoft.com/en-us/kb/976064
mkramer777Author Commented:
When I plug in both monitors to the existing video card with 2 ports Windows does not see the 2 monitors.  It says 2nd monitor is not detected.    The instructions are for a laptop which in my case works every time.  it's the desktops that are more difficult sometimes.
Tim PhillipsWindows Systems AdministratorCommented:
Sometimes there are strange settings in the BIOS regarding video output.  Might want to check that out.  If you see a "video out" setting, set it to PCIE instead of onboard to get full use of the video card.
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Can you try updating both video drivers with the latest version and make sure the refresh rate on both monitors are set to what each video card can support.  So both monitors never came on at the same time at any time at all during POST, O.S bootup, etc?
Tim PhillipsWindows Systems AdministratorCommented:
It's ok if they don't both come on at the same time.  You need only one during POST.  Did you check the BIOS for the setting I was mentioning?
mkramer777Author Commented:
I will check the BIOS
Scott CSenior EngineerCommented:
What is the make/model of the video card?  Knowing what hardware we are talking bout will be a big help.
mkramer777Author Commented:
Video card: Promo AMD Radeon HD 8490 PCIe 3.0 x16 Graphics Card, 1GB DDR3

Computer:  HP ProDesk 400
mkramer777Author Commented:
I have a side question.  I have put 2 monitors on another computer that has a video card with a vga port and a dvi port.  The monitors work just fine but the dvi connected monitor looks kind of streaky.  That is the only word I can say it looks like.  I have put another monitor (a brand new one) with a dvi port on this computer and it does the same exact thing.  Looks streaky with a hint of pink that is barely noticeable.  Any ideas on this?
Scott CSenior EngineerCommented:
Check cables?  possible a broken wire inside or a bent pin.

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Displays / Monitors

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