I am running a network version of Prism 5, and can't view the help file. It comes on screen, but the table-of-contents links don't actually work and I see the message "Action cancelled".

What's going on?

Prism help is compiled into a CHM file, which is installed on the server in the same folder with the Prism.exe application. These kinds of files (which are the standard way Windows applications provide Help)  are viewed with the Microsoft Help Viewer, which is basically an extension of Internet Explorer. Other browsers cannot open CHM files. CHM files can include macros, so can be a security risk. However,  Prism's  help file does not include any macros. Because of the potential risk of macros, Windows security is wary of letting someone view a CHM on the network. So you have to do some configuration.

The problem was created by Microsoft, as documented  here and here and here (newest). 

We create our help files using a tool called Help And Manual. Here is their explanation and workarounds for the problem of accessing help over networks.

A work around

The entire Prism 5 help system is posted on our web site. The contents are identical, but of course the web site won't be linked to buttons in the program. View the Help on the web.

Prism 5 Windows solves the problem automatically

We have tried hard to make Prism 5 solve this problem on its own.  This happens automatically, and you don't need to do anything special. Prism checks the registry settings. If they are not set correctly, it runs the program fixchm.exe which is located inside the Prism folder. This may prompt the UAC dialog. If you OK that dialog, then fixchm.exe runs and sets the regisry as it needs to be. This requires administrator rights. Once you once run Prism with admin rights (and OK, not cancel, the UAC dialog), Prism should run fine without admin rights in the future.
 

Prism 5 Windows -- manual tweaks

If you use Windows Vista or Windows 7, quit Prism, make sure you are logged in with admin rights, start the program fixchm.exe (which is in the Prism folder) and then restart Prism. 

Fixchm.exe fixes the registry entry as explained below.

If you use Windows Vista or Windows 7, you may also consider turning UAC off. (If you don't know what the UAC is, consider yourself lucky and skip this step!)

If those two steps did not solve the problem,  try the following steps. These involve editing the registry, which is something only computer geeks should try, and only when they are unrushed and super careful.  

1. Login as administrator.
2. Run regedit. Select Run from the Start menu.
3. Open the appropriate registry key, which differs for 32 and 64 bit versions of WIndows:
     For 32bit systems:
       HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\ItssRestrictions
   
     For 64bit systems:
       HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\HTMLHelp\1.x\ItssRestrictions
    
4. Find the value "UrlAllowList".
5. The path to prism5.chm should exist in the list. If not, then add it.

Notes on the UrlAllowList:

• Each path in this list must be separated by ";".
• The last item in the list must be "file://;"
• You must list the full path and file name, not just the path. 

Here is an example:

UrlAllowList=P:\\Software\Windows7\Prism5.03\Prism5.chm;file://

Note that this works only if you map the drives, and refer to the drive with its mapped letter ( "P:" in the example above). It will not work if you try to use syntax like this:

           \\mycompany.com\ Software\Windows7\Prism5.03\Prism5.chm;file://

Prism 4 Windows
If you use a network license for Prism 4, a security patch to Windows XP issued in summer 2005 prevents launching help (.chm) files over a network.

You can download a utility that will make the registry changes for you here:

http://www.ec-software.com/products_hhreg.html

To use the utiilty, open it and select Add File. Then browse to the folder on the your network where Prism is installed and select the Prism4.chm file. Close the HHReg window and you should be able to access the Prism help files. You will need to run this utility on each network computer.