I have a simple textured wall, and it looked really clean so I downloaded a grungy texture from CG. Unfortunately, when I tried making the alpha channel invisible, I couldn't figure it out, so I just turned the alpha under the textures panel to 0 and enabled mask transparency which I turned down to 3.14 (cause pi is cool). Its not exactly the effect I want, because some of the white from the mask still discolors the wall, but the biggest problem is once I deselect it, it turns the entire wall transparent.
Here is what it looks like while selected: almost right
but once I deselect.
What is the proper way to make the alpha channel disappear, while leaving the moldy-grunge intact and not making a gaping hole in my wall. This is a game prop.