Some Microsoft HTML Help projects include merged .CHM files used to create binary indexes. This type of index combines keywords from multiple compiled help files (.CHM files) into one master help file. Each .CHM remains its own project, but the keywords from each index file are combined into the master project.
You should remove .CHM files that become obsolete or are no longer needed in the master project.
Open the master project that includes the .CHM file to remove.
From the File menu, select Project Settings.
Click the Index tab.
Click the Advanced tab.
From Merged Files, select the .CHM you no longer need to use.
Click Remove.
Click OK to save the project settings.
Compile the master project to update it.