Alright, I'll simplify then.
Use this picture with my poorly constructed example below. (btw I had way to much fun making this XD)http://www.bsninc.com/images/PC_back.png
| <- power cord connection
(__)| <- fan vent
| <- The motherboard panel.
| <- motherboard slots added to the board, this is where your
| current card is installed.
(the reason its not straight is because it keeps changing style sizes sorry about that disregard the white x's)
In the picture, the blue spots that are found in both the motherboard panel and the motherboard slots are VGA slots.
What you can do if you have both is plug into the motherboard connection instead of the graphic card since the graphic card doesn't work right now.
Sometimes the graphics card will still try to take priority so what you need to do is disable the graphic card only if this happens
. You can do this via the device manager in safe mode.
To get to the device manager do the following.
For xp Operating systemshttp://pcsupport.about.com/od/windowsxp/f/opendmxp.htm
For Windows 7http://pcsupport.about.com/od/windows7/f/open-device-manager-windows-7.htm
Once there You should see a "Display Adapter" tab
Open it and it should show you your graphics card there.
Right click and disable it. Then use the motherboard port.
If it works then its the graphics card, if it doesn't then its something else entirely.
Also its possible you don't have a motherboard built in video port (like vga) in which case you can't do this to find out if the graphics card isn't working.