Uses ShlObj, ComObj;

procedure TForm1.Button1Click(Sender: TObject);
const CLSID_ActiveDesktop: TGUID= '{75048700-EF1F-11D0-9888-006097DEACF9}';
var
ActiveDesktop: IActiveDesktop;
begin
ActiveDesktop:= CreateComObject(CLSID_ActiveDesktop)as IActiveDesktop;
ActiveDesktop.ApplyChanges(AD_APPLY_ALL or AD_APPLY_FORCE);
end;