If your graphics card is not detected by Windows, there are several possible solutions that you can try in order to get it working again.
1. Ensure your graphics card is fully seated in its slot.
Check that your graphics card is properly seated and all connections are firmly in place. Make sure the card is securely inserted into the correct slot — AGP for an AGP card and PCI-Express for a PCI-Express card. You should also make sure that any adapters or power cables are properly connected to your card.
2. Disable and re-enable the graphics card in the Device Manager.
In the Device Manager window, click on the arrow beside Display Adapters to expand the list of available devices. Right click on your graphics card and select Disable. Once the card is disabled, select Enable from the same context menu. Restart your computer and check to see if the device has been detected.
3. Uninstall and reinstall the graphics card drivers.
Open the Device Manager window and right click on your graphics card. Select Uninstall Device, then restart your computer. Upon restarting you can access the manufacturer website and download the most recent drivers for your card. Install the drivers and restart the computer once more. Once completed, check to see if Windows has detected your graphics card.
4. Revert to an older driver version.
If the latest version of your graphics card’s driver is causing issues, you may need to revert to an older version. To do this, open the device manager, right click on your graphics card, select Uninstall Device, then restart your computer. Go to the manufacturer’s website and download an older version of the driver. Install the driver, restart the computer, and check to see if your graphics card is now detected.
5. Check the system requirements for your graphics card.
Make sure your computer meets or exceeds the system requirements for your specific graphics card. If it does not, then the card may not be compatible with your system.
6. Check the power supply.
If your graphics card requires additional power from the power supply, make sure the power supply is properly connected and providing the necessary levels of power. In some cases the power supply may not be supplying the appropriate levels of power.
7. Replace the graphics card.
If all else fails, replacing the graphics card may be the only solution. Make sure you purchase a card that is compatible with your system and meets its power requirements.
If none of these solutions work in getting your graphics card detected by Windows, contact the manufacturer of the card for additional assistance.