procedure TForm1.BitBtn1Click(Sender: TObject);
var s:string;
begin
SetLength(s, MAX_PATH);
SHGetSpecialFolderPath(0, PChar(s), CSIDL_DRIVES, false);
shellExecute(handle,nil,pchar(s),'','',SW_Show);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
 Pidl: PItemIDList;
 ExeInfo: TShellExecuteInfoW;
begin
 if Succeeded(SHGetSpecialFolderLocation(0, CSIDL_DRIVES, pidl)) then
   begin
     ZeroMemory(@ExeInfo, SizeOf(ExeInfo));
     ExeInfo.cbSize := SizeOf(ExeInfo);
     ExeInfo.fMask := SEE_MASK_INVOKEIDLIST ;
     ExeInfo.lpVerb := nil;
     ExeInfo.nShow := SW_SHOWNORMAL; //SW_SHOW
     ExeInfo.lpIdList := Pidl;
     ExeInfo.Wnd := 0;

     ShellExecuteExW(@ExeInfo);

     CoTaskMemFree(Pidl);
   end;

end;