[Gemma]

Search for this code in the arcade.php file

$this->output .= "<div align='center'>".$rating."<br />";
				$this->output .= "<a href=\"#\" onclick=\"window.open('{$ibforums->base_url}act=Arcade&amp;do=rate&amp;gid={$gid}&amp;scored=1','comment_edit','height=150,width=400'); return false;\">{$ibforums->lang['rate_game']}</a></div><br /><br />";
			}

And change the height and/or width accordingly