How do I combine an alpha and a solid texture

After studying the tutorials (which are great btw, thanks), and spending some time practicing, at last i figured out the alpha channels.

Now i would like to place an alpha texture on top of a solid texture, and that i really can not figure this out... (a typical example would be to place a window in a wallpaper texture, ) I know i can start over and cut the alpha texture and do it this way, but I guess there has to be a simpler solution since the alpha texture already has the vital pixels marked.

I would really appreciate an advice on this

It is just a matter of editing it in Photoshop, or some other app that handles .tga files, like Gimp.

What I do is open the file for the wall, and if it has the art on the background layer, duplcate the layer so you get a copy that will be transparent if you cut part of it away. Then copy the pic of the window and paste it into a new layer in the wall file. Scale the window as needed, and position it. Select a rectangle on the wallpaper layer that matches where the window glass is, and cut that away on the wallpaper layer. Leave a little overlap between the window frame itself and the wallpaper. In the Layers pallette, right click the icon for the layer where the window is, and select "Select Layer Transparency". Use that for the alpha mask, as shown in Chip's sticky tutorial on alpha textures.

You now have an alpha map for the window, but the area outside the window frame is also transparent! So edit the alpha layer and solid fill where the rest of the wall is.

Last, put an all-black layer nehind the other two layers, to eliminate any white halo in the window glass area.

That is it.