If you are using Windows operating system in your computer, then you are very much aware about the DLL file of the Windows. Actually DLL files are responsible for the proper running of any applications in the Windows computer. But sometimes when you try to run an application, you may get dxdiagn.dll is missing error in Windows. It is a very critical error issue that comes to you due to the missing or corrupt dxdiagn.dll file. After the occurring of the error issue, you will not be able to access the application associated with this DLL file properly. You may also lose the important data from the computer. So it is very important to fix this issue with the help of the troubleshooting tips given in this article. You can also fix the issue automatically with the help of Advanced System Repair tool.