I've created a CHM file for my app with popup topics. I've made a reference to the CHM file in the Project Properties section of my app and I've set all the HelpContextID numbers for the context sensitive help--I've also noticed that the What's This button doesn't seem to want to show with a sizable form so I've added a What's This? menu item and used the .WhatsThisMode method. The problem is that the only response I'm getting from the app where the help is concerned is an error message saying that it can't open the help file. This error is only occuring on a form that has a fixed border with the What's This button on the captionbar. I'm not getting any response whatsoever on the main form. Any ideas? I can't even get the file to open using the ShellExecute API eventhough it is a registered file type and I can double click on it to open it using Explorer.