DLL-Downloads.com has an excellent tutorial that demonstrates how to install .DLL files in Windows. What is a .DLL? Glad you asked. DLLs are packages that contain code and data that are used by multiple programs on your computer. Occasionally when you remove a program that shares a .DLL with other applications, the shared .DLL will incorrectly get removed, too. If a .DLL is missing you'll get an error along the lines of, "Error opening file, dllName.dll missing."
Fortunately, the process of installing .DLLs is pretty easy. In a nutshell, all you need to do is copy the original .DLL file to
C:\Windows\System32. Once the .DLL is copied over, run the following command:
regsvr32 filename.dll and your .DLL will be successfully installed. The tutorial works perfectly well on Windows XP and Windows Vista.