Index: typo3/install/index.php
===================================================================
--- typo3/install/index.php	(revision 10516)
+++ typo3/install/index.php	(working copy)
@@ -34,8 +34,48 @@
  * @subpackage core
  */
 
+/**
+ * Displays an error message and stops execution of the script
+ *
+ * @param array $markers The markers which should be displayed in the text
+ * @return void
+ */
+function installToolErrorMessage($markers) {
+		// Include t3lib_div and t3lib_parsehtml for templating
+	require_once($GLOBALS['PATH_site'] . '/t3lib/class.t3lib_div.php');
+	require_once($GLOBALS['PATH_site'] . '/t3lib/class.t3lib_parsehtml.php');
 
+		// Define the stylesheet
+	$stylesheet = '<link rel="stylesheet" type="text/css" href="' .
+		'../stylesheets/install/install.css" />';
+	$javascript = '<script type="text/javascript" src="' .
+		'../contrib/prototype/prototype.js"></script>' . LF;
+	$javascript .= '<script type="text/javascript" src="' .
+		'../sysext/install/Resources/Public/Javascript/install.js"></script>';
 
+		// Get the template file
+	$template = @file_get_contents($GLOBALS['PATH_site'] . '/typo3/templates/install.html');
+		// Define the markers content
+	$markers = array_merge($markers, array(
+		'styleSheet' => $stylesheet,
+		'javascript' => $javascript,
+	));
+		// Fill the markers
+	$content = t3lib_parsehtml::substituteMarkerArray(
+		$template,
+		$markers,
+		'###|###',
+		1,
+		1
+	);
+		// Output the warning message and exit
+	header('Content-Type: text/html; charset=utf-8');
+	header('Cache-Control: no-cache, must-revalidate');
+	header('Pragma: no-cache');
+	echo $content;
+	exit();
+}
+
 // **************************************************************************
 // Insert some security here, if you don't trust the Install Tool Password:
 // **************************************************************************
@@ -58,8 +98,24 @@
 $enableInstallToolFile = $PATH_site . '/typo3conf/ENABLE_INSTALL_TOOL';
 
 	// If typo3conf/FIRST_INSTALL is present and can be deleted, automatically create typo3conf/ENABLE_INSTALL_TOOL
-if (is_file($quickstartFile) && is_writeable($quickstartFile) && unlink($quickstartFile)) {
-	touch($enableInstallToolFile);
+if (is_file($quickstartFile)) {
+
+	if ((is_writeable($quickstartFile)) && (is_writable($PATH_site . '/typo3conf/'))) {
+		unlink($quickstartFile);
+		touch($enableInstallToolFile);
+	} else {
+			// typo3conf is not writable. Display an error
+			$markers = array(
+				'title' => '"typo3conf" folder is not writable',
+				'content' => '
+					<p>
+						The TYPO3 Install Tool requires the typo3conf/ folder to be writable. Please change the rights accordingly and reload this page.
+					</p>
+				'
+			);
+
+			installToolErrorMessage($markers);
+	}
 }
 
 	// Only allow Install Tool access if the file "typo3conf/ENABLE_INSTALL_TOOL" is found
@@ -75,24 +131,8 @@
 
 	// Change 1==2 to 1==1 if you want to lock the Install Tool regardless of the file ENABLE_INSTALL_TOOL
 if (1==2 || !is_file($enableInstallToolFile)) {
-		// Include t3lib_div and t3lib_parsehtml for templating
-	require_once($PATH_site . '/t3lib/class.t3lib_div.php');
-	require_once($PATH_site . '/t3lib/class.t3lib_parsehtml.php');
 
-		// Define the stylesheet
-	$stylesheet = '<link rel="stylesheet" type="text/css" href="' .
-		'../stylesheets/install/install.css" />';
-	$javascript = '<script type="text/javascript" src="' .
-		'../contrib/prototype/prototype.js"></script>' . LF;
-	$javascript .= '<script type="text/javascript" src="' .
-		'../sysext/install/Resources/Public/Javascript/install.js"></script>';
-
-		// Get the template file
-	$template = @file_get_contents($PATH_site . '/typo3/templates/install.html');
-		// Define the markers content
 	$markers = array(
-		'styleSheet' => $stylesheet,
-		'javascript' => $javascript,
 		'title' => 'The Install Tool is locked',
 		'content' => '
 			<p>
@@ -117,20 +157,8 @@
 			</p>
 		'
 	);
-		// Fill the markers
-	$content = t3lib_parsehtml::substituteMarkerArray(
-		$template,
-		$markers,
-		'###|###',
-		1,
-		1
-	);
-		// Output the warning message and exit
-	header('Content-Type: text/html; charset=utf-8');
-	header('Cache-Control: no-cache, must-revalidate');
-	header('Pragma: no-cache');
-	echo $content;
-	exit();
+
+	installToolErrorMessage($markers);
 }