Jane,
The path that you specify in the Program Parameters field
should match the actual path to the topic file inside the CHM. For
example, if you've compiled the topic file into an "html" folder
within the CHM then the path would be:
ms-its:voipgenerators.chm::/
html/sip001.htm
To double-check what the path is, open the target topic in
the CHM, right-click the topic pane, and then click Properties on
the context menu. The address shown in the Address (URL) field is
the absolute path to the topic file.
Pete