DLL files contain vital information about Windows and your PC's hardware configuration. Opening these files can allow experienced users to potentially troubleshoot issues within Windows but should not be attempted by those without experience, as it is easy to make a mistake and damage your operating system. "Windows Shell Common DLL" is associated with the shell32.dll file.
Log in to Windows as an administrator if your normal user profile does not have those privileges.
Click on the Start icon in the lower left corner of the desktop and type "shell32.dll" into the search box. Press "Enter."
Click on the "Open with" button in the Caution box that pops up. In the next dialogue box, choose "Select a program from a list of installed programs."
Click on "Notepad" in the Open With window. Click to uncheck the box next to "Always use the selected program to open this kind of file. Click "OK" to open the file.
It is very important to uncheck the "Always use the selected program" box described in Step 5. Not doing so could cause Windows errors. As the numerous warning boxes indicate, opening a DLL file is not something to be taken lightly and can have serious consequences for your computer. Don't do it unless you're an experienced user and know what you're doing. Notepad might be useful for viewing the contents of a DLL file but is not recommended for editing.