function RegisterExt(const AExt, AId, ADescription, AExeFilePath,
AIconGroup : string): boolean;
var
  Reg: TRegistry;
begin
  Result := true;
  Reg := TRegistry.Create;
  with Reg do
  try
    CloseKey;
    RootKey := HKEY_CLASSES_ROOT;
    try
      OpenKey(AExt, true);
      WriteString('', AId);
      CloseKey;
      OpenKey(AId, true);
      WriteString('', ADescription);
      CloseKey;
      if AExeFilePath<>'' then
      begin
        OpenKey(AId + '\shell\open\command', true);
        WriteString('', '"' + AExeFilePath + '" "%1"');
        CloseKey;
      end;
      OpenKey(AId + '\DefaultIcon', true);
      WriteString('', AIconGroup);
      CloseKey;
    except on E: ERegistryException do
      Result := false;
    end;
  finally
    Reg.Free;
  end;
end;