You have cleaned your PC, and now each time you start it or try to access a specific application, your system informs you of an error related to File Extension DLL. What has happened? Probably you have deleted a file with a DLL extension, which you shouldn't have done.
DLL files are Windows libraries, needed to store the links libraries that the operating system needs to be able to run specific applications, or just to share information among them. And now how can you recover this deleted DLL?
To answer that question and solve your problem, you have two options. One is to reinstall your complete operating system, with drivers. The second is more simple: download, totally for free, and install this File Extension DLL.