ah, ok.... to make a transparency map (the thing that goes in the alpha channel), you need white where its not at all transparent and black where it is totally transparent. If you put it as grey (like what you've done by the sounds of it - i.e. using the texture map as the transparency map).... then it'll all be partially transparent which is what you're seeing in the right picture. So, you've got to make a transparency map for the hair, which is white where you want no transparency.... and put that in.

Dreams are just nightmares on prozac...
Digital WasteLanD