uses shellapi

function deldir(dir: String): boolean;
var fos: TSHFileOpStruct;
begin
ZeroMemory(@fos, SizeOf(fos));
with fos do begin
wFunc := FO_DELETE;
fFlags := FOF_SILENT or FOF_NOCONFIRMATION;
pFrom := PChar(dir+#0);
end;
Result:=(0=ShFileOperation(fos));
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
deldir('c:\a');
end;