Gamers are the people who mostly need high graphics so it is a need that they should know how much graphics they have in order to check system requirements of games which they will get or for some other purpose. It is a common trick but many are anaware of it. 
Press the start button to get started. Now type "dxdiag" without brackets. You will find a result which is like the result shown here.You will have to select it.
After selecting it a window will appear from where you have to select the display tab.After selecting the display tab you will see a box appear. In the box the graphics details will be given.
I have given the part where the graphics details will be displayed in a red rectangle. In the image given above the graphics written is 785Mb. So you can find your graphics memory like this.You can also use this window to get information about many other things. KEEP VISITING. . . . . . . . . . ....