Your COMMDLG.DLL file could be missing due to accidental deletion, uninstalled as a shared file of another program (shared with Windows), or deleted by a malware infection. Furthermore, COMMDLG.DLL file corruption could be caused from a power outage when loading Windows, system crash while loading COMMDLG.DLL, bad sectors on your storage media (usually your primary hard drive), or quite commonly, a malware infection. Thus, it's critical to make sure your anti-virus is kept up-to-date and scanning regularly.
Commdlg.dll Could Not Be Installed Windows 7