<?php
$act = $HTTP_GET_VARS['act'];

if( $_POST['pass'] == '12345' ): //coloca a senha ali...
	if ( $act == 'start' ):
		$output = shell_exec("./Server.exe start");
		echo $output;
	elseif ( $act == 'stop' ):
		$output = shell_exec("./Server.exe stop");
		echo $output;
	endif;
else:
?>
<form name="form1" method="post" action="?act=<?php echo $act; ?>">
	<label for="pass"></label>
	<input type="text" name="pass" id="pass">
	<input type="submit" name="button" id="button" value="OK">
</form>
<?php
endif;
?>