This version of the terrain multitexturing shader needs at least Pixel Shader v1.4 and uses Vertex Shader 1.1.

Terrain Multitexturing Shader for PS 1.4

The idea with it is to allow the use of more than (3) textures and using all channels of the alpha TGA seperately to map out and blend the textures.

I have only tested it on the setup in my signature.