I read somewhere with windows 7 if you can add a dual pci-e video card to the computerand window 7 will also read the original video output of the computer allowing you to use 3 monitors with just a additional video cards ? Any one tried this.
With Windows XP through 7 you can run multiple video cards and have a single extended desktop. I don't know whether your first video adapter is on the motherboard or an add-in card. But my belief is that in either case you can use a second adapter, and probably as many extra adapters as you have available slots. Adapters may (or must, I don't know) allocate a chunk of main memory, so memory available for apps could be reduced. I have run 4 monitors for years, using two PCI ATI cards originally, and now one dual-nvidia pci-e card.
well the computer i have now has Vista and only 1 pci-e slot and 3 regular small pci slots . And i want to run 3 monitors. i was going to buy a dual card off a guy but he said with vista once you put in a video card it cuts off the origianal video card on the motherboard .
No, because in general the on boad crap is one thing: crappy. We either use it, or a seaprate one. THen we get PowerColor 5770's Eyefinity 5 now. 5 ports for 5 monitors 1gb ram, decent price. Even develoeprs using only 2 screens now get that card - the savings are not worth the trouble of replacing cards when we need a third monitor at one point.
It seems you have an onboard video on your computer. As soon as you add an external dual video card on the bus, your onboard video will most likely be disabled, leaving you with 2 video outputs for 2 monitors. To drive 3 monitors, may need to get 2 dual video cards. Or use a USB-to-VGA/DVI adapter for the third monitor.
^ This answer is spot on. I prefer a low end second video card over a USB adapter because of performance reasons. With a USB adapter the screen can freeze up from time to time. Here's the adapter I have: http://www.newegg.com/Product/Product.aspx?Item=N82E16815101001 For a video card you will need to see what type of empty slots you have PCI-E or PCI and a low end card will be plenty good enough as long as you are not playing HD Videos on that screen.
@watchdaride You can certainly do that - your on-board video will not be disabled if you add extra video card. Also, unless you play high-end fps games, that video card doesn't even have to be latest/expensive. For desktops, there's absolutely no need to waste money on usb video card when an internal one would do a better job for less money. P.S. Check motherboard video ports again - you may have two already. I do (VGA + HDMI on a 3+ year old ASUS motherboard) and 2 monitors attached (24" + 19"), working like a charm for everything. So once you get that video card, you may be able to plug 4 monitors. Hope this helps.
For most PCs the onboard won't work if you use a video card. I actually tried to do this a few weeks back (get the onboard working) but it just cannot be done, on dell machines at least. I've only got 1 PCI Express slot so also tried adding one of the old style video cards (non PCI Express) and nearly broke the whole machine. The only way is to have 2 (of the same) PCI Express video cards installed and then you should be able to run 4 monitors. But even that might run into trouble with some machines.
Nvidia allows 2 out of 3 outputs to run at the same time (you usually get 3 plugs on a card, like DVI, VGA, HDMI or whatever). ATI cards may not have this problem - an old setup I just replaced had 3 monitors running at once - DVI and VGA off an ATI card and the mobo VGA also active. If you get 2 Nvidia, try and get the same GPU, since that way you can set them up with a SLI interconnect - each GPU takes part of the rendering load - for when/if you want to play games (not that you have to play games, but it's nice to know you could with decent output onto 2 of the monitors - SLI supports only 2 at the moment).