How to modify the default Web browser and e-mail client programmatically in Windows XP (299853)

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By default, Windows XP uses a global setting in the HKeyLocalMachine (HKLM) Registry key to set an initial, default e-mail and Web browser client from the Start menu. Windows XP also implements new registry keys in HKeyCurrentUser (HKCU) to store individual internet and e-mail client information for each user as part of their profile if users select a different client than the default. The following code sample adds a Web browsing and e-mail client to the available options on the system and shows how to modify both the global and the current user:

1. Create a new Microsoft Visual Basic "Standard EXE" project.
2. Add a module to the project by right-clicking the project name in the Project Explorer window.
3. Double-click the new module that you created, and then paste the following code into the code module:

Const REG_SZ As Long = 1
Const HKEY_CURRENT_USER = &H80000001
Const HKEY_LOCAL_MACHINE = &H80000002
Const KEY_SET_VALUE = &H2
Const KEY_ALL_ACCESS = &H3F
Const REG_OPTION_NON_VOLATILE = 0
Const HWND_BROADCAST = &HFFFF
Const WM_SETTINGCHANGE = &H1A

Declare Function RegCloseKey Lib "advapi32.dll" _
  (ByVal hKey As Long) As Long
Declare Function RegCreateKeyEx Lib "advapi32.dll" _
  Alias "RegCreateKeyExA" (ByVal hKey As Long, _
  ByVal lpSubKey As String, ByVal Reserved As Long, _
  ByVal lpClass As String, ByVal dwOptions As Long, _
  ByVal samDesired As Long, ByVal lpSecurityAttributes As Long, _
  phkResult As Long, lpdwDisposition As Long) As Long
Declare Function RegOpenKeyEx Lib "advapi32.dll" _
  Alias "RegOpenKeyExA" (ByVal hKey As Long, _
  ByVal lpSubKey As String, ByVal ulOptions As Long, _
  ByVal samDesired As Long, phkResult As Long) As Long
Declare Function RegSetValueExString Lib "advapi32.dll" _
  Alias "RegSetValueExA" (ByVal hKey As Long, _
  ByVal lpValueName As String, ByVal Reserved As Long, _
  ByVal dwType As Long, ByVal lpValue As String, _
  ByVal cbData As Long) As Long
Declare Function SendMessage Lib "user32" _
  Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, _
  ByVal wParam As Long, lparam As String) As Long
Public Function SetClient(iClient As Integer, sDisplayName As String, _
  sClientCommandLine As String, sClientResourceDLL As String, _
  iLocalization As Integer, bGlobalClient As Boolean, _
  Optional sCLParameters As String, Optional bMakeDefault As Boolean) As Integer
  
  ' iClient - 1 for internet browser, 2 for e-mail client
  ' sDisplayName - the name to be displayed on the menu for the client
  ' sClientCommandLine - the path and filename of the e-mail client
  '
  ' The next two parameters are included for localization of the client.
  ' For backwards compatibility with applications that do not support localized
  ' strings, the name of the application in the installed language should be set
  ' as the Default value for the key.
  ' sClientResourceDLL - provides a path to an EXE or DLL containing the
  '   localized strings for the client.
  ' iLocalization - a string resource ID within the DLL whose value is
  '   to be displayed to the user allowing the same registration to
  '   be used for multiple languages.  For each language, provide a
  '   different Resource DLL, and the dynamic loading of the string
  '   from the DLL results in the correct strings being displayed, depending
  '   on the language.
  '
  ' bGlobalClient - sets the value for either all users (True) or the
  '   current user (False)
  ' sCLParameters - additional parameters on the command line to be passed to the
  '   browser or e-mail client.
  ' bMakeDefault - (Optional) set the browser or e-mail application as the default
  
  Dim iStatus As Integer
  Dim hHandle As Long
  Dim hGRegKey As String
  Dim hLRegKey As String
  Dim sCommand As String
  Dim sKey As String
  Dim sAll As String
  Dim sRoot As String
  Dim hKey As Long
  Dim sLoc As String
  hGRegKey = HKEY_LOCAL_MACHINE
  hLRegKey = HKEY_CURRENT_USER
  
  If iClient = 1 Then
    sRoot = "Software\Clients\StartMenuInternet"
  Else
    sRoot = "Software\Clients\Mail"
  End If
  
  ' Create and null terminate needed strings
  sCommand = "shell\open\command"
  sKey = sRoot & "\" & sDisplayName
  sAll = sKey & "\" & sCommand
  sLoc = "@" & sClientResourceDLL & "," & iLocalization & Chr$(0)
  sClientLocation = """" & sClientCommandLine & """" & _
    IIf(sCLParameters <> "", " ", "") & Trim(sCLParameters) & Chr$(0)
  sDisplayName = sDisplayName & Chr$(0)
  
  ' Create a registry key for the new client
  iStatus = RegCreateKeyEx(hGRegKey, sKey, 0&, vbNullString, _
    REG_OPTION_NON_VOLATILE, KEY_ALL_ACCESS, 0&, hNewKey, lRetVal)
  iStatus = RegCreateKeyEx(hGRegKey, sAll, 0&, vbNullString, _
    REG_OPTION_NON_VOLATILE, KEY_ALL_ACCESS, 0&, hNewKey, lRetVal)
  If iStatus = ERROR_NONE Then
    iStatus = RegOpenKeyEx(hGRegKey, sAll, 0, KEY_SET_VALUE, hKey)
    iStatus = RegSetValueExString(hKey, "", 0&, REG_SZ, sClientLocation, _
      Len(sClientLocation))
    iStatus = RegCloseKey(hKey)
    iStatus = RegOpenKeyEx(hGRegKey, sKey, 0, KEY_SET_VALUE, hKey)
    iStatus = RegSetValueExString(hKey, "", 0&, REG_SZ, sDisplayName, _
      Len(sDisplayName))
    ' Add the localization string
    iStatus = RegSetValueExString(hKey, "LocalizedString", 0&, REG_SZ, _
        sLoc, Len(sLoc))
    iStatus = RegCloseKey(hKey)
  Else
    SetClient = iStatus
    Exit Function
  End If
  
  '  Sets browser as local or global default if specified
  If bMakeDefault Then
    If bGlobalClient Then
      iStatus = RegOpenKeyEx(hGRegKey, sRoot, 0, KEY_SET_VALUE, hKey)
      iStatus = RegSetValueExString(hKey, "", 0&, REG_SZ, sDisplayName, _
        Len(sDisplayName))
      iStatus = RegCloseKey(hKey)
    Else
      iStatus = RegCreateKeyEx(hLRegKey, sRoot, 0&, vbNullString, _
        REG_OPTION_NON_VOLATILE, KEY_ALL_ACCESS, 0&, hNewKey, lRetVal)
      iStatus = RegSetValueExString(hNewKey, "", 0&, REG_SZ, _
        sDisplayName, Len(sDisplayName))
      iStatus = RegCloseKey(hNewKey)
    End If
    UpdateMenus
  End If
End Function
Private Sub UpdateMenus()
  ' Refresh the menu choices with the updated client
  Dim iRetVal As Integer
  iRetVal = SendMessage(HWND_BROADCAST, WM_SETTINGCHANGE, 0, _
    "SOFTWARE\Clients\mail")
  iRetVal = SendMessage(HWND_BROADCAST, WM_SETTINGCHANGE, 0, _
    "SOFTWARE\Clients\StartMenuInternet")
End Sub

You can call the functions in the module from a form. Here are some examples of calling this function.

Dim x As Integer
'  Sets up a browser for the current user and makes it default
x = SetClient(1, "My Browser", "C:\Program Files\MyBrowser\mybrowser.exe", "C:\Program Files\MyBrowser\localization.dll", -123, True, "-homepage", False)
'  Sets up an e-mail client for the current user and makes it default
x = SetClient(2, "My E-mail", "C:\Program Files\MyEmail\myemail.exe", "C:\Program Files\MyEmail\localization.dll", -456, True, "-inbox", False)