dx9.dll 相关的错误可能源于多种不同原因。比如，错误的应用程序、 dx9.dll 被删除或放错位置、被您 PC 上存在的恶意软件破坏、损坏的 Windows 注册表等。
最常出现的错误信息是：
- 程序无法启动，因为您的计算机缺少 dx9.dll 。尝试重新安装程序来解决这个问题。
- 启动 dx9.dll 发生错误。无法找到指定的模块
- 加载 dx9.dll 发生错误。无法找到指定的模块
- dx9.dll 的设计可能不适合在 Windows 上运行，或可能包含错误。
在绝大多数情况下，解决方案是在您的 PC 上正确地重新安装 dx9.dll 到 Windows 系统文件夹。 此外，有的程序，特别是 PC 游戏，要求 DLL 文件放置在游戏/应用程序安装文件夹。
获取详细安装指南，请查看我们的 FAQ 。
关于 dx9.dll 的其他信息：
[2014-03-26] This page is the wiki page for the file Dx9.dll.
Are you getting an error for "Failed to load DX9 DLL"?
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This error is referring to a "DX9 dll", a dll-file installed by DirectX 9, and not the file "dx9.dll"
How to solve this error for South park - The stick of truth, in Steam;
Find out what DLL is the problem.
Go to the game folder (eg. "C:\Program Files\Steam\SteamApps\common\South Park - The Stick of Truth\") and run "South Park - The Stick of Truth.exe" outside of the Steam client. You should get a separate error message that will tell you what DLL is broken.
Find the missing file at www.dll-files.com , Download and install.
alternatively, download the latest direct x redistributable from msdn and it should then work..