Firefox gets its protocol information from the Windows registry.

1. Open Notepad.
2. Copy one of the following blocks of code and paste it in Notepad. (Click the + to show the code):

Open aim: addresses with AOL Instant Messenger 5.9

• REGEDIT4
  
  [HKEY_CLASSES_ROOT\aim]
  @="URL:aim Protocol"
  "URL Protocol"=""
  
  [HKEY_CLASSES_ROOT\aim\shell]
  
  [HKEY_CLASSES_ROOT\aim\shell\open]
  
  [HKEY_CLASSES_ROOT\aim\shell\open\command]
  @="\"C:\\Program Files\\AIM\\aim.exe" \"%1\""

Open aim: addresses with AOL Instant Messenger 6.5

• REGEDIT4
  
  [HKEY_CLASSES_ROOT\aim]
  @="URL:aim Protocol"
  "URL Protocol"=""
  
  [HKEY_CLASSES_ROOT\aim\shell]
  
  [HKEY_CLASSES_ROOT\aim\shell\open]
  
  [HKEY_CLASSES_ROOT\aim\shell\open\command]
  @="\"C:\\Program Files\\AIM6\\aim6.exe" ee://aol/imApp/ \"%1\""

Open msnim: addresses with MSN Instant Messenger or Windows Live Messenger

• REGEDIT4
  
  [HKEY_CLASSES_ROOT\msnim]
  @="URL:msnim Protocol"
  "URL Protocol"=""
  
  [HKEY_CLASSES_ROOT\msnim\shell]
  
  [HKEY_CLASSES_ROOT\msnim\shell\open]
  
  [HKEY_CLASSES_ROOT\msnim\shell\open\command]
  @="\"C:\\Program Files\\Internet Explorer\\iexplore.exe\" \"%1\""

• This will use Internet Explorer to open MSN Messenger or Windows Live Messenger. There is no currently known way to make Firefox open the program directly and perform the correct action.

Anything else

• REGEDIT4
  
  [HKEY_CLASSES_ROOT\myprotocol]
  @="URL:myprotocol Protocol"
  "URL Protocol"=""
  
  [HKEY_CLASSES_ROOT\myprotocol\shell]
  
  [HKEY_CLASSES_ROOT\myprotocol\shell\open]
  
  [HKEY_CLASSES_ROOT\myprotocol\shell\open\command]
  @="\"C:\\Program Files\\My Program\\program.exe\" \"%1\""

• Replace the word "myprotocol" with the protocol Firefox gave you. (There are five instances to replace.) Replace the path the path in the last line (starting after @="\" and ending before \" \"%1\"") with the path to the program you want to run. When writing the path, you need to double all backslashes.

Once you have the correct code:

1. Save the file as protocol.reg onto your Desktop.
2. Double click the file on your Desktop.
3. (Vista) The User Account Control dialog may appear. Click Continue.
4. A Registry Editor dialog will appear asking if you want to continue. Click Yes.
5. Click OK.

Now that the protocol has been registered, try the link again. You may get an External Protocol Request dialog. Click Launch Application. The program you chose should now start.

Firefox gets its protocol information from its hidden settings.

1. Type about:config in the Location Bar and press EnterReturn.
2. Right-clickHold down the Ctrl key while you click anywhere in the grid, choose New, then String.
3. In the Enter the preference name prompt, type in network.protocol-handler.app.myprotocol (replacing myprotocol with the protocol you want to register) and press OK.
4. In the Enter string value prompt, type the path to the program you want the protocol to start and press OK.

Now that the protocol has been registered, try the link again. You may get an External Protocol Request dialog. Click Launch Application. The program you chose should now start.

• Still not working? Make sure that the path you put in the preference is correct. Due to a bug in Firefox, entering an incorrect path will give you the same error message.