Add items to the Windows Explorer right-click menu

Problem/Question/Abstract:

How do I add some items to Explorer's right-click menu, which appears when the user right-clicks on a certain file type?

Answer:

procedure add_context_menu;
type
  extns = (wav, png, bmp, jpg);
const
  ext_names: array[extns] of string = ('.wav', '.png', '.bmp', '.jpg');
var
  ext: extns;
  reg: TRegistry;
  name: string;
  command: string;
begin
  reg := TRegistry.Create;
  reg.RootKey := HKEY_CLASSES_ROOT;
  {Build the command string we want to store}
  command := '"' + Application.ExeName + '" "%1"';
  {Loop over extensions we can handle}
  for ext := wav to jpg do
  begin
    {See if this extension is already known in HKEY_CLASSES_ROOT}
    if reg.OpenKeyReadOnly('\' + ext_names[ext]) then
    begin
      name := reg.ReadString(''); {Get the name of this type}
      if name <> '' then
        {If not blank, open this type's shell key, but don't create it}
        if reg.OpenKey('\' + name + '\shell', False) then
          {Try to create a new key called "APTprocess". Note that for Delphi5 we
          need to set the access explicitly}
          reg.Access := KEY_READ or KEY_WRITE;
      if reg.OpenKey('APTprocess', True) then
      begin
        {The default value will be displayed in the context menu}
        reg.WriteString('', '&APT process');
        {So now open the command key, creating it if required}
        reg.Access := KEY_READ or KEY_WRITE;
        if reg.OpenKey('command', True) then
          {and write the command string as the default value}
          reg.WriteString('', command);
      end;
    end;
  end;
  reg.Free;
end;