So you are running win6 aka Vista, an what graphics card are you using? dx9 is well really old and i have no acces to hardware in my shop under dx11.
win xp sp2 dx9 all updated Geforce 7025 / nividia nforce 630a version 6.14.0013.0790
Ok, XP thats old. well these Hardeware i do have that old somwhere with DX9 Support but building up a PC for that is a bit to much. x'D
I think just that old OS is your Problem for that Unity Game. My the Dev's be with you.^^
