My corpo computer opened the chm (I could see the tree on the left), but won't open content (standard IE message on the right). I fixed the problem by right-clicking on the .chm file, "properties" then click on the "unblock" button (maybe not unblock, my windows is in french... the button is near the read-only check box in the file properties). It disable the run-protection for files from internet, then I can read the chm properly now. Thanks Eltorro, great job.