Graphics card question

You don't. It isn't possible.

 

Here's why...sometimes it's helpful to know WHY... instead of just getting the quick answer. On a portable machine, it's impossible to just swap the graphics card.

On the MacBook, the video chip is what's called an "integrated" chip. It's soldered to the Logic Board and shares the system RAM, instead of having its own dedicated RAM to use for video processing.

On the MacBook Pro, you still can't replace just the video card because the video processor chip (in my case nVidia 8600GT) is still soldered to the logic board, but it is a standalone video processor with standalone RAM that is dedicated to just graphics stuff, and not shared with the system.

Thats the difference, and why you can't replace the cards. It's like this on PC's and Macs.