If you have a program like photoshop or paintshop than you can make, what is known as a heightmap. That is a picture that shows the height ifference of the ground. It should look something like this: http://www.c-unit.com/tutorials/directx/images/Terrain/heightMap.jpg

You save it as bmp. Open MED and open the heightmap. Med will turn the picture in a 3d model. Then after you have added a texture you save it as terrain and you can use it in games.

There are programs though. I use Freeworld 3d, but that costs $30, don't know about free ones.