I have the frontbuffer with a completely drawn scene. I want to update only a small part of the scene without redrawing the entire scene from scratch... I guess I could do that by copying the frontbuffer to backbuffer and updating only the necessary scene part. Still, I don't know how to copy the frontbuffer to backbuffer... Any help would be appreciated!

http://www.ugrad.cs.ubc.ca/~cs414/opengl/glDrawBuffer.html

Try 'flipping' the buffers and then just draw over your old buffer. glDrawBuffer switched which on you are drawing on.

What do you exactly mean by "flipping" ? Is it SwapBuffers() ?

It'll be great if you would post some example code on how to do this...