Extract the contao zip archive with this script.

install.php

<?php

/**
 * PHP version 5
 *
 * Extracts the Contao archive (downloaded from contao.org) and redirects to the install tool.
 *
 * Usage:
 * * Upload this file and the Contao archive in the desired folder
 * * Run this script
 *
 * @author    Richard Hen
 * @license   LGPL
 * @copyright Richard Hen 2013
 */
// Prevent server run out
ini_set('memory_limit', '72M');
ini_set('max_execution_time', 160);

// Variables
$absolutePath = realpath('./');
$arrArchives = glob('*.zip');
$strSubdirectory = dirname($_SERVER["SCRIPT_NAME"]);

if (@class_exists('ZipArchive'))
{
	/**
	 * Extract archive
	 */
	$zip = new ZipArchive();

	if ($zip->open($arrArchives[0]) !== TRUE)
	{
		die ('Could not open archive');
	}

	$zip->extractTo($absolutePath);

	// Define variables before close zip
	$strContaoVersion = dirname($zip->getNameIndex(2)); /* contao-x.y.z.zip */
	$arrObjects = scandir($absolutePath . '/' . $strContaoVersion);

	$zip->close();

	/**
	 * Copy subdirectory's content to ROOT
	 */
	foreach ($arrObjects as $object)
	{
		if ($object != '.' && $object != '..')
		{
			rename($absolutePath . '/' . $strContaoVersion . '/' . $object, $absolutePath . '/' . $object);
		}
	}
	// Delete empty subdirectory
	rmdir($absolutePath . '/' . $strContaoVersion);

	/**
	 * Redirect to install tool
	 */
	if (strlen($strSubdirectory) > 1)
	{
		header('Location: http://' . $_SERVER["SERVER_NAME"] . $strSubdirectory . '/contao/install.php');
	} else
	{
		header('Location: http://' . $_SERVER["SERVER_NAME"] . '/contao/install.php');
	}

	// Delete remains
	unlink($arrArchives[0]);
	unlink(__FILE__);
}
else
{
	// ZipArchive does not exist
	die ('ZipArchive() is necessary and not available on your web server.');
}