Vob or Dvd won't use DirectShow or AC3

Hi.
I use Vista Ultimate 64 bit and windows media player + K-lite Mega codec pack (32+64).

Usually i don't have problem about filters or audio on vista (i love vista), but when i try to open .vob or dvd files windows media player won't use DirectShow audio or AC3filter and the sound is a little lower than usual.

If i rename the .vob file into .mp4 it works.

I'd like it to use AC3 filter automatically without renaming. How can i do that ?

I wait for your advices.
Bye

Ok i got it, vob and dvd use cyberlink or microsoft decoder ...

but can i apply a sound filter while using syberlink decoder just like i do when i use directshow decoder?