How to refresh the icon cache

uses
  Registry;

function RefreshScreenIcons : Boolean;
const
  KEY_TYPE = HKEY_CURRENT_USER;
  KEY_NAME = 'Control Panel\Desktop\WindowMetrics';
  KEY_VALUE = 'Shell Icon Size';
var
  Reg: TRegistry;
  strDataRet, strDataRet2: string;

 procedure BroadcastChanges;
 var
   success: DWORD;
 begin
   SendMessageTimeout(HWND_BROADCAST,
                      WM_SETTINGCHANGE,
                      SPI_SETNONCLIENTMETRICS,
                      0,
                      SMTO_ABORTIFHUNG,
                      10000,
                      success);
 end;


begin
  Result := False;
  Reg := TRegistry.Create;
  try
    Reg.RootKey := KEY_TYPE;
    // 1. open HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics
    if Reg.OpenKey(KEY_NAME, False) then
    begin
      // 2. Get the value for that key
      strDataRet := Reg.ReadString(KEY_VALUE);
      Reg.CloseKey;
      if strDataRet <> '' then
      begin
        // 3. Convert sDataRet to a number and subtract 1,
        //    convert back to a string, and write it to the registry
        strDataRet2 := IntToStr(StrToInt(strDataRet) - 1);
        if Reg.OpenKey(KEY_NAME, False) then
        begin
          Reg.WriteString(KEY_VALUE, strDataRet2);
          Reg.CloseKey;
          // 4. because the registry was changed, broadcast
          //    the fact passing SPI_SETNONCLIENTMETRICS,
          //    with a timeout of 10000 milliseconds (10 seconds)
          BroadcastChanges;
          // 5. the desktop will have refreshed with the
          //    new (shrunken) icon size. Now restore things
          //    back to the correct settings by again writing
          //    to the registry and posing another message.
          if Reg.OpenKey(KEY_NAME, False) then
          begin
            Reg.WriteString(KEY_VALUE, strDataRet);
            Reg.CloseKey;
            // 6.  broadcast the change again
            BroadcastChanges;
            Result := True;
          end;
        end;
      end;
    end;
  finally
    Reg.Free;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  RefreshScreenIcons
end;