There are a number of reasons responsible for the d3dx9_43.dll missing error. Some of them are: outdated device drivers, corrupted Windows system files, installation and uninstallation of the latest programs or games corrupt the d3dx9_43.dll files, virus or malware infection, the apps or games is outdated.
Generally, the DLL files are located in C:WindowsSystem32 folder. And the d3dx9_43.dll file is also situated in the Window system folder (C:WindowsSystem32 folder). Moreover some games also requires that the DLL file should be placed in the game/application installation folder.
The File D3dx9 43dll For Resident Evil 6