DirectX 9.0c is the last version available for Windows 98/ME/2000/XP users, so to avoid alienating that vast userbase many companies are still releasing games based on the older version. If the game won't run with DirectX10 installed you can still install DirectX 9.0c alongside v10.x and each game will use the appropriate one.
I have a new machine happily running (really!) Vista SP1 with DirectX10. But games and now Microsoft Worldwide Telescope seem to be telling me they require DirectX 9.0c. What the...?
I assume the two don't run concurrently. I also assume downloading v9.0c will trash my Vista graphics, which I like.
Any help, suggestions, illumination? Thanks.