Here is how to set up the package.
Step 1:Search for theWindows End-User Runtimesdownload package online.
Step 2:Choose the appropriate language for your PC, then clickDownload.

Step 3:Once youve downloaded the file, run it and follow the on-screen instructions to install it.
Step 4:After the package is installed, you should power cycle your rig.
Then, check to see if the problem has been resolved.

Thus, you had better refresh your gear drivers to fix the issue.
Lets see how to update the driver.
Step 1: Right-click theStartbutton and selectDevice Manager.
Step 2: Double-click theDisplay adapterscategory to view your rig.
Step 3: Right-click your graphics card and chooseUpdate driver.
Step 4: In the pop-up window,choose Search automatically for updated driver software.
Then follow the wizard to finish the left steps.
Once its done, it’s crucial that you restart the computer to make the changes to take effect.
Then you’re able to check to see if the issue still exists.
Step 1: Click theStartmenu.
Right-clickCommand Promptand chooseRun as administrator.
Step 2: When you get intoCommand Prompt, inputsfc /scannowand pressEnter.
Step 3: Then Windows will scan for system file issues.
you gotta wait until the process is 100% completed.
Now exit Command Prompt and restart the computer.
The d3dx9_42.dll is missing error should disappear.
If you come across the same issue, it’s possible for you to try these solutions.