When an application requires mscomctllib.ocx, Windows will check the application and system folders for this OCX file. If the file is missing you may receive an error and the application may not function properly.
.OCX Error Example
Run-time error '336': Component 'mscomctllib.ocx' or one of its dependencies not correctly registered: a file is missing or invalid.
Possible fixes for mscomctllib.ocx errors.
Re-Install the application that requires mscomctllib.ocx.