That's a bit of a shame that you have to do that to get through a large map. I'll have to check what size I'm playing on atm because I've had very few problems and it seems rather large.
I think RAM might be a limiting factor at times, especially with only 2GB, and it's a nice easy thing to upgrade, so don't abandon your idea.
Oh and press Print Screen to take a screenshot. It saves it somewhere in your ".../Documents/My Games/.../Screenshots" folder as a .tga file.