I have an AMD Radeon Hd7800 Series Graphics Card, I am trying to connect 4 basic monitors up. I have 3 working but am unable to get the fourth. I don't know how many monitors I can hook up with this card? I can't find anything online and there is no phone number to contact tech support to verify if I can even connect 4 monitors.
How can I find out how many monitors I can have connected to this card?
There are enough connections on the card for 4 monitors>
Since you didn't post the Make & Model of your HD78XX it may be difficult to answer your question.
I would download GPU-Z and run it and see which HD78xx you actually have installed.
But guessing I used a Sapphire HD 7850 GPU card and the maximum supported Monitors is "3".
While a XFX HD7870 supports 4 Monitors.
Also the Sapphire HD7870 Flex supports 6 Monitors.
So depending on which HD78xx you have and the manufacturer will depend how many monitors it will support from 3 to 6 Monitors.
Edit: On some of the older GPU cards, You can only plug in one Monitor to two same ports. Sometimes 2 Ports (HDMI or DVI) may share the same chip so if you plug in one monitor on one HDMI port the other HDMI port will be disabled.