Faces transparent from 1 side

I’m using blender 2.49b. some faces can only be seen frhttp://gyazo.com/4c172f62425053a00f33170f25ed6a01.pngom 1 side. How do i fix this?

I have no idea how to fix that, but I have to ask why are you using 2.49? Not being a wiseguy, I just am curious.