SurClaro Flight Simulator Resources

I am wondering if someone could answer a question? I have a Dell Inpiron 1100 laptop ( yes you are thinking , "My God, this mor is trying to run FS on a laptop." Just wait, it gets better.) with 256 mb of memory and about a 1.8 ish gig processor. FS runs about 10 fps with the current display settings I have. I am preparing to upgrade to 640 mb of memory. Will this be a big improvement? What about going to 1024 mb of memory? Is there a limit of memory that will help FS? Or will 1024 be even better than 640? I have found some low priced memory from a reputable seller but I cant just buy the memory and return it if it doesnt help all that much. Any help would be helpful. (well duh) Thanks alot! Shocked