I have had this problem before, and managed to fix it then, but do not remember how. I recently had to reinstall the GECK for Fallout 3. When I try to open it I get the message, "The program can't start because d3dx9_38.dll is missing from your computer. Try reinstalling the program to fix this problem." Of course, reinstallation does not fix anything. Additional reinstalls only return the same error message. Anyone remember what to do to fix this?

Thanks

By the way, I am having a similar problem with the new vegas geck, saying it has missing files.

D3dx9_38.dll issues are caused in one way or another by an issue with Microsoft DirectX. The d3dx9_38.dll file is one of many files contained in the DirectX software collection. Since DirectX is utilized by most Windows based games and advanced graphics programs, d3dx9_38.dll errors usually show up only when using these programs.D3dx9_38.dll errors appear when a game or other software program is started.

Troubleshooting Steps:

1. Restart your computer if you haven't yet. The d3dx9_38.dll error might be a fluke and a simple restart could clear it up completely.

2. http://www.microsoft.com/en-us/download/search.aspx?q=directx. Chances are, upgrading to the latest version of DirectX will fix the d3dx9_38.dll not found error.

Note 1: 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 2: The same DirectX installation program works with all versions of Windows including Windows 7, 8, Vista, 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 d3dx9_38.dll error you're receiving, look for a DirectX installation program on your game or application CD or DVD. Usually, if a game or other program utilizes DirectX, the software developers will include a copy of DirectX on the installation disc. Sometimes, though not often, the DirectX version included on the disc is a better fit for the program than the latest version available online.

4. Restore the d3dx9_38.dll file from the latest DirectX package. If the above troubleshooting steps haven't worked to solve your d3dx9_38.dll error, try extracting the d3dx9_38.dll file individually from the DirectX package.

5. 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.