You need more RAM and I'd say a Gfx card update should be in your near future as well. The larger all abundant maps can use almost all of the 2GB of RAM alotted to 32bit programs, so the game is dipping into the swap file probably causing some of the slowdown. The zoomed in slowdown is being exxagerated by the dated Gfx card also I believe. Short of an upgrade, you'll just need to keep turning down options. Some of the biggies are planet surface variety, specular intensity, and for me(before I upgraded) the ships showing in orbit would cause slowdown, but you'll just have to fiddle till you can get somewhat of a satisfactory experience. Good Luck