It has nothing to do with DX9 redist, it's just dependencies. It's either installed (game starts) or not (game does not starts).
Guess it's 7900 personal issue only, I remember ppl who played Risen were having many issues as well, like, fog was white and non-transparent, etc...
The only possible (but unlikely) cure it to jiggling with different drivers versions, like, 17x.xx, 16x.xx, 18x.xx, etc...
