pH7: The particular version he linked to (v9.0c) has fixed graphics related problems for me earlier - and I had the latest version of DirectX (10 or 11 - can't remember) already installed (Vista 64). Seems like some older games didn't stick to the official API and guidelines making newer versions not backwards compatible enough. Or something. Anyway, I suggest giving it (v9.0c) a try.
Some of the components of Directx9 are not included in Directx10 or 11. This causes some games to not work if they depend on some of these components. This is why you need to install the most up to date version of Directx9 on a Win 7 machine (not sure about Vista), since Win7 does not come with Directx9 included by default.
*edit* Apologies if you already know this. Your post seemed to indicate you're not sure why installing DX9 helped solve some of your game issues.