If you've already downloaded x3daudio1_7.dll from one of those DLL download sites, remove it from wherever you put it and continue with these steps.
1 Restart your computer if you haven't yet.
The x3daudio1_7.dll error might be a fluke and a simple restart could clear it up completely.
2 Install the latest version of Microsoft DirectX. Chances are, upgrading to the latest version of DirectX will fix the x3daudio1_7.dll not found error.
Note: Microsoft often releases updates to DirectX without updating the version number or letter so be sure to install the latest release even if your version is technically the same.
Note: The same DirectX installation program works with all versions of Windows including Windows 7, Windows Vista, Windows XP, and more. It will replace any missing DirectX 11, DirectX 10, or DirectX 9 file.
3 Assuming the latest DirectX version from Microsoft doesn't fix the x3daudio1_7.dll error, look for a DirectX installation program on your game or application DVD or CD. Sometimes the software developers will include a copy of DirectX on the installation disc if their game or program utilizes DirectX.
Sometimes, though not often, the DirectX version included on the disc is a better fit for the program than the latest version available from Microsoft.
4 Uninstall the game or software program and then reinstall it again. Something might have happened to the files in the program that work with x3daudio1_7.dll and a reinstall could do the trick.
5 Restore the x3daudio1_7.dll file from the latest DirectX software package. If the above troubleshooting steps haven't worked to solve your x3daudio1_7.dll error, try extracting the x3daudio1_7.dll individually from the DirectX downloadable package.
6 Update the drivers for your video card. While it's not the most common solution, in some situations updating the drivers for the video card in your computer could correct this DirectX issue.