Game Installation says I don't have DirectX 9+ on my Vista

[Jack]

I tried installing Marvel's Ultimate Alliance, but I can't play it
because it's telling me that "DirectX 9.0c is not installed on this
computer." - even though DirectX 10 is installed. Does anyone have a
clue as to why I'm getting this message?

 

[Jeff]

Jack,

Even though Vista has direct X 10, some games need specific files, like
the monthly updated dx9 ones, also even if you do have them, some games just
don't read it correctly in Vista.
I've ran into that lots-and just let the game install the direct x 9 it
needs, or if it doesn't come with a dx9 installer for the specific files, I
went to MSFT's downloads and grabbed them, then installed the game.

Jeff

 

[Jack]

thanks. I don't know much about directx, but if I let the game install
directx 9, am I possibly downgrading my experience for other games?
Or do the directx 9 files not write over the directx 10 files and I
would just be installing a few directx9 files that seem to be required
for this particular game, but overall I would still have directx 10?