chm viewer unable to show contents

Other than what Nicolas suggested, you may not be able to see contents of a CHM that you open over a UNC path. If that is the case copy the file to a local drive.

Try to right-click on your chm file and select properties. You will see an "Unblock" button. Click on it, it should solve your problem.

On Windows 7 copying the file locally and unchecking the file opening warning message worked.

just go to power shell and run it as administrator, cd your folder

and use the following command Unblock-File '.\filename.chm'