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I know there are a few questions here that ask about dual monitors but my problem is a little different. My desktop has only one DVI monitor input. I am using the DVI monitor input for my current monitor. I have another monitor which uses VGA.

I am hoping that I could have dual monitor for my computer, like I could extend my computer's screen space to two-monitor space.

The problem, however, is since my desktop only has one DVI monitor input; I can only use one monitor at any one time. Also, one of my monitors uses DVI and the other uses VGA. Most Y-Splitters come in the form of either both DVI or both VGA.

What should I do in my case if I still want to have dual monitor display?

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Twice you have written "desktop only has one DVI monitor input". If "desktop" means computer, then the PC would have a DVI monitor output, not an input. The signal goes from the PC out to the monitor. BTW would you recognize a VGA port or HDMI port if your PC had those? –  sawdust Aug 30 '12 at 5:57
    
My PC only has a DVI and HDMI port. –  xenon Aug 30 '12 at 6:18
    
@xEnOn wait... so it does have two outputs, an HDMI and a DVI? In that case, get a DVI-VGA adapter, and an HDMI-DVI adapter. DVI and HDMI are compatible, and DVI and VGA are compatible. HDMI is not compatible with VGA though. –  nhinkle Aug 30 '12 at 8:50
    
DVI and VGA are not always compatible. DVI-I is compatible, DVI-D is not. –  Hennes Aug 30 '12 at 14:35
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5 Answers

up vote 2 down vote accepted

Best and most reliable option is to buy a new graphics card if you have a spare slot. Graphics over USB is woeful. Watching content that refreshes quickly (ie, Video) is not worth it. The cheaper end of graphics cards however are generally quite acceptable. Choose one that supports DVI-I, then you can use a DVI/VGA adaptor for your VGA monitor, later being able to use it for DVI if needed.

A Y-Split will not extend, only duplicate the signal (unless you have a dual DVI port) however I doubt this.

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Thanks! In case I understand wrongly, I could simply buy a cheap VGA PCI graphics card to put into my computer and have the DVI monitor plugged into the original graphics card and the VGA monitor plugged into the cheap graphics card, am I right? –  xenon Aug 30 '12 at 5:24
    
Yep, you certainly can do that :) I simply suggested buying one with a DVI output, and then using a DVI/VGA adaptor in case you wanted to use it in the future with your current or another DVI only monitor. –  Trissy Aug 30 '12 at 5:24
    
I just opened up my computer and realised that it has only one graphics card slot. The other available slots are all PCI. I have 2 old graphic cards but they are all uses AGP. Not sure if this getting a PCI graphics card with DVI will be a problem. :( –  xenon Aug 30 '12 at 6:21
    
PCI and PCI-E graphics cards are readily available with VGA and/or DVI –  Trissy Aug 30 '12 at 6:24
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If you have a DVI connector and a HDMI connector already on your computer then chances are that all you need is an adapter to take the HDMI "port" and convert it to DVI. Leave the existing DVI connector and monitor alone. Just connect an adapter to your computers HDMI port to change it to DVI and then connect your other monitor. I think sawdust posted some excellent pictures of what these adapters look like. That last one looks like it's exactly what you want too: HDMI-to-DVI

Then it's just a matter of possibly BIOS settings and driver tweaking.

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My PC only has a DVI and HDMI port.

Then maybe you do not need a second graphics adapter.

Most PCs that have no VGA connector usually have a DVI-I interface; both DVI and VGA signals are available at the pins. If you use a DVI-to-VGA adapter, then you would be able to connect your VGA monitor.

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Then if you used a HDMI(male)-to-DVI adapter at the PC (or HDMI cable w/HDMI-to-DVI adapter at the monitor), you could connect the DVI monitor.

enter image description here

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If I don't need a second graphics card, with the VGA-to-DVI connector, I could only use one monitor but not extending my screen's space to two monitors. Or I still could? –  xenon Aug 30 '12 at 7:23
    
You would need to use a DVI-to-VGA adapter, not a "VGA-to-DVI connector". You have not provided any specifics (What is the installed graphics card? What is the OS?) But it could be possible to use one graphics adapter with two monitors, with the desktop extended across the two screens. For Windoze: microsoft.com/athome/organization/… –  sawdust Aug 30 '12 at 8:42
    
You might already have a DVI-to-VGA adapter. I've always received one with equipment that came with a DVI-I port. –  sawdust Aug 30 '12 at 8:56
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I'd put a usb splitter set it up for vga and connect the other monitor to normal dvi.

http://www.tigerdirect.ca/applications/SearchTools/item-details.asp?EdpNo=4266219&CatId=467

** note you can buy cheaper ones then above just regular cord with a vga connection on the end.

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Buy another graphics card, or a USB monitor. A Y-splitter is going to duplicate the signal, not make two serparate monitors.

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USB video adapter should be a last resort. They use proprietary drivers and dont update fast. If you have a free PCI slot, a cheap video card is still the better choice. –  Keltari Aug 30 '12 at 4:53
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