opengl resize window/image help?

I’ve finally been able to use the alpha blend function with opengl. I’ve created an image and then for testing, i’ve drawn a few semi-transparent polygons on top of that image. it works, but when i go to resize the window, my semi-transparent polygons does not get resized, only the main image underneath. Is there a way to find out what size pixel the client window is at and then somehow force opengl to draw at that size? i will also need to plot some points later on.

Thanx in advance for any help/suggestions.

ps. i’m using msvc++ 6.0 on NT(sp4).