As well as incorrect, duplicate, or missing registry entries there are many other problems that may befall the DLLs on your system. It is possible to recover from virtually any error, but it may require some work, and may also mean a loss of functions in some programs. One of the leading causes of problems is an incorrect DLL version being called, and this can occur frequently. It may require the installation of several versions of a DLL, although most are backwards compatible.
Missing DLL - this means that a call has been made by an application for a particular DLL. However, that DLL could not be found. In some cases this means that the DLL file in questions can not be found on your system. However, when a DLL is called, the application must provide a path to that library.
As such, a missing DLL error can occur in cases where the actual DLL name does not match the name of the DLL being called. It may also mean that the path that is being called does not match the actual path of the eisting DLL. The DLL may be on your system, but it is possible that it could have an incorrect name or be in the incorrect location. This could be an error with the DLL itself or with the coding of the application causing the error.