Welcome to the Aces High Forum, and the TE Topic.
.raw files can't be opened with paint, or any other graphics program to my knowledge without a plugin. There must be a way somewhere, perhaps Photo Shop, I don't know. You will probably need either GIMP or PS (a free license is available for personal use) at some point.
L3DT Pro, a $50.xx(?) 3rd party program has been recommended by HTC as a way to manipulate .raw files.
Artik's program is a fast way to generate a terrain and get started but there are some important TE import steps the beginner might miss. I think it's covered in his README file so unless you already have a project in mind, that's where you could start.