alpha

where is the alpha butten so the black uv becomes transperant?
in blender 2.5

Im not sure what button you are talking about. you know where it was in 2.49 ? UV face? You can assign a material to the face in the material window and there add alpha .
Hope that helps ya a little.

within the texture buttons, open the ‘image sampling’ tab, and under ‘alpha’ click ‘calculate’.