I have a graphics problem help plz!!!!!

[WIndows7 Player]

I got the Civilization 4 the complete edition and every time a play anyone it shows a message saying "Failed to allocate video memory.Please try reducing the graphics settings and Runtime Error!. I lower it to the lowest graphics and it still does that someone plz help me.
P.S. I played civ3 and got this game so you might have to explain to me step my step and easy way to understand. PPPPPPPLLLLLZZZZZZ.​

 

[bwcbwc]

What graphics card are you using? Go into Windows Device manager and select "Display Adapters" to see the graphics (assuming your drivers are installed).