Thank you for all your computer hardware suggestions, as well as your criticism. In response to Azelor's question, the mountains were actually sculpted by hand in GIMP. I created a detailed and realistic mountain texture in Wilbur, then miniaturized it for use in GIMP as a brush. I realize the mountain ranges are out of scale (rather large) for this conworld, assuming it has the same dimensions as the Earth; however, I'm severely limited by my processor and RAM. In placing the mountain ranges on my middle continent, I tried to duplicate North America's general scheme--Rockies near the west coast and the Appalachians near the east. The other continents I just varied that basic scheme in a random way, but that randomness might have been unwise. And in response to Pixie's suggestion, I will certainly try to eliminate the canyons at low altitudes on my next map, using larger settings for Incise Flow before finally computing the rivers. By the way, I've decided to go with 16 Gb of RAM and a large solid state drive, and skip the video card. Thanks again for everyone who offered a suggestion, for I strive to get better at producing high-quality atlas-style maps. I believe it's a highly underrated art form.