|If the video card has a power socket on it, you MUST connect a wiring connector from the PS, that fills the socket, to it !|
Your main chipset probably has the Hybrid video feature.
In that case, by default, you often get no video from the card in the slot yet your onboard video still works.
You need to change settings in the bios Setup to enable the video on the card in the slot.
Generically, this is the info I have provided about this topic previously:
You change the settings when the monitor is connected to the enabled onboard video.
Once the settings have been saved and the computer reboots, hold the power button in until the computer shuts off, switch off the monitor, plug it into the port on the card in a slot, switch on the monitor, boot the computer.
" Some recent and fairly recent mboards have a "Hybrid" video feature where if you install certain specific video chipset cards, the onboard video is NOT disabled when you install the PCI-E X16 card in a slot - both video adapters work. If you install a PCI-E X 16 card that has a video chipset that is NOT compatible with that "hybird" feature, the onboard video is NOT disabled by installing a PCI-E x16 card in a slot, and by default, the card in the slot produces no video. In that case, you have to connect a monitor to the onboard video, and go into the bios and set Primary Video or Initialize Video First or similar to PCI-E or similar, Save bios settings, and only THEN the onboard video is disabled and the PCI-E X16 card produces video. "
The setting may not be PCI-E specifically - e.g. it was PEG in a bios for a Gigabyte mboard I loooked up, but you get the idea.
You found the setting to disable the onboard video, which you CANNOT do in bioses on mboards that don't have the Hybrid capability (if it doesn't have the Hybrid capability the bios auto disables the onboard video when you install a card in a PCI-E X16 slot) , but you need to find this other one I mentioned