Index: install.php
===================================================================
--- install.php	(revision 13329)
+++ install.php	(working copy)
@@ -1181,6 +1181,30 @@
 		}
 
 		/**
+		 * Virtually place module under "modules" folder or it won't be recognized during upgrade to 5.1.0 version
+		 *
+		 * @param string $name
+		 * @param string $path
+		 * @param string $version
+		 * @return string
+		 */
+		function getModulePath($name, $path, $version)
+		{
+			if ($name == 'Core') {
+				// don't transform path for Core module
+				return $path;
+			}
+
+			$version = $this->toolkit->ConvertModuleVersion($version);
+
+			if ($version < $this->toolkit->ConvertModuleVersion('5.1.0')) {
+				return 'modules/' . $path;
+			}
+
+			return $path;
+		}
+
+		/**
 		 * Returns list of modules, that can be upgraded
 		 *
 		 */
@@ -1194,7 +1218,9 @@
 					continue;
 				}
 
+				$module_info['Path'] = $this->getModulePath($module_name, $module_info['Path'], $module_info['Version']);
 				$upgrades_file = sprintf(UPGRADES_FILE, $module_info['Path'], 'sql');
+
 				if (!file_exists($upgrades_file)) {
 					// no upgrade file
 					continue;
Index: install/install_toolkit.php
===================================================================
--- install/install_toolkit.php	(revision 13329)
+++ install/install_toolkit.php	(working copy)
@@ -310,6 +310,7 @@
 			$sqls = str_replace('CREATE TABLE ', 'CREATE TABLE IF NOT EXISTS ' . $table_prefix, $sqls);
 			$sqls = str_replace('DROP TABLE ', 'DROP TABLE IF EXISTS ' . $table_prefix, $sqls);
 			$sqls = str_replace('<%TABLE_PREFIX%>', $table_prefix, $sqls);
+			$sqls = str_replace('<%PRIMARY_LANGUAGE%>', $this->Application->GetDefaultLanguageId(), $sqls);
 
 			if (isset($replace_from) && isset($replace_to)) {
 				// replace something additionally, e.g. module root category
@@ -591,12 +592,17 @@
 		/**
 		 * Returns information about module (based on "install/module_info.xml" file)
 		 *
-		 * @param string $module_folder
+		 * @param string $module_name
 		 * @return Array
 		 */
-		function getModuleInfo($module_folder)
+		function getModuleInfo($module_name)
 		{
-			$info_file = MODULES_PATH . '/' . $module_folder . '/install/module_info.xml';
+			if ($module_name == 'core') {
+				$info_file = FULL_PATH . '/' . $module_name . '/install/module_info.xml';
+			}
+			else {
+				$info_file = MODULES_PATH . '/' . $module_name . '/install/module_info.xml';
+			}
 
 			if (!file_exists($info_file)) {
 				return Array ();
@@ -625,22 +631,22 @@
 		/**
 		 * Returns nice module string to be used on install/upgrade screens
 		 *
-		 * @param string $module_folder
+		 * @param string $module_name
 		 * @param string $version_string
 		 * @return string
 		 */
-		function getModuleString($module_folder, $version_string)
+		function getModuleString($module_name, $version_string)
 		{
 			// image (if exists) <description> (<name> <version>)
 
 			$ret = Array ();
-			$module_info = $this->getModuleInfo($module_folder);
+			$module_info = $this->getModuleInfo($module_name);
 
 			if (array_key_exists('name', $module_info) && $module_info['name']) {
 				$module_name = $module_info['name'];
 			}
 			else {
-				$module_name = $this->getModuleName($module_folder);
+				$module_name = $this->getModuleName($module_name);
 			}
 
 			if (array_key_exists('image', $module_info) && $module_info['image']) {