Navigation to the webpage was canceled
When you download a CHM file or a ZIP archive containing a CHM file with IE 7, you get an error message when you try to open the help file. The message is "Navigation to the webpage was canceled" or "Dieses Programm kann die Webseite nicht anzeigen." on a German OS. This error message is part of Microsoft's attempt to make Windows more secure. After all, if you don't read the help files, you don't know all the variations of damaging your system.
Afterwards the help file can be opened. If you are testing Guineu, please perform these steps for the ZIP file.