I'm suprised that terrain doesn't work for you. I managed to create one without crashing with my photoshop CS3. I don't know do you still have problems with it, but just look at replies, member made tutorials and manual, I'm sure you will figure out then. Now, my real problem is texture, when I load my map's terrain it's always on greyscale, I can't use any colors. Well, I'll have to try! ^^"
~LittleWolf~