I had some chm files that I've always been able to open and read. However, recently I moved them to other folders when all of a sudden I was not able to view the individual pages in these files. I got a page cannot be displayed error. It turns out that the reason is that I placed these chm files in a folder that had a "#". These were C# books, so I created a folder called "C#"and placed the chm files in this folder. This is what caused my problem. Once I renamed the folder to "C Sharp" I was able to open the chm files.