diff --git a/README b/README
index d7095c8a..5b0f6cac 100644
--- a/README
+++ b/README
@@ -48,6 +48,7 @@ martinambrus changes:
 36. fixed OK message in Admin when resetting All Players' PLUS
 37. new config option to show Support messages in Admin's mailbox
 38. new feature: allowing messages to be sent as Support from in-game when user is Admin + it's allowed in config
+39. not allowing installation if old data are still in database to prevent multiple worlds generation and game misbehavior
 
 
 Shadowss changes:
diff --git a/install/include/oasis.php b/install/include/oasis.php
index 32e01f0c..da3048b0 100644
--- a/install/include/oasis.php
+++ b/install/include/oasis.php
@@ -9,10 +9,13 @@
         include ("../../GameEngine/Database.php");
         include ("../../GameEngine/Admin/database.php");
 
-
-		$conn = mysqli_connect(SQL_SERVER, SQL_USER, SQL_PASS);
-		mysqli_select_db($conn, SQL_DB);
-
+		// check if we don't already have world data
+		$data_exist = $database->query_return("SELECT * FROM " . TB_PREFIX . "odata LIMIT 1");
+		if (count($data_exist)) {
+		    header("Location: ../index.php?s=6&err=1");
+		    exit;
+		}
+		
 		$database->populateOasisdata();
 		$database->populateOasis();
 		$database->populateOasisUnits2();
diff --git a/install/include/wdata.php b/install/include/wdata.php
index 628aa56c..76f2c137 100644
--- a/install/include/wdata.php
+++ b/install/include/wdata.php
@@ -12,6 +12,12 @@
 
 include("database.php");
 
+// check if we don't already have world data
+$data_exist = $database->query_return("SELECT * FROM " . TB_PREFIX . "wdata LIMIT 1");
+if (count($data_exist)) {
+    header("Location: ../index.php?s=3&err=1");
+    exit;
+}
 
 $xyas=(1+(2*WORLD_MAX));
 
diff --git a/install/templates/field.tpl b/install/templates/field.tpl
index 812b2000..99e478f9 100644
--- a/install/templates/field.tpl
+++ b/install/templates/field.tpl
@@ -16,7 +16,11 @@
 #################################################################################
 
 if(isset($_GET['c']) && $_GET['c'] == 1) {
-echo "<div class=\"headline\"><span class=\"f10 c5\">Error creating wdata. Check configuration or file.</span></div><br>";
+echo "<br /><hr /><br /><div class=\"headline\"><span class=\"f10 c5\">Error creating wdata. Check configuration or file.</span></div><br><br>";
+}
+
+if(isset($_GET['err']) && $_GET['err'] == 1) {
+echo "<br /><hr /><br /><div class=\"headline\"><span class=\"f10 c5\">Existing World Data found in the database! Please clear your database before continuing.</span></div><br /><br />";
 }
 ?>
 <form action="process.php" method="post" id="dataform">
diff --git a/install/templates/oasis.tpl b/install/templates/oasis.tpl
index 85d8f52e..a67cc68e 100644
--- a/install/templates/oasis.tpl
+++ b/install/templates/oasis.tpl
@@ -1,4 +1,4 @@
-<?
+<?php
 //////////////////////////////////////////////////////////////////////////////////////////////////////
 // TRAVIANX //
 // Only for advanced users, do not edit if you dont know what are you doing! //
@@ -6,6 +6,11 @@
 // - TravianX = Travian Clone Project - //
 // DO NOT REMOVE COPYRIGHT NOTICE! //
 //////////////////////////////////////////////////////////////////////////////////////////////////////
+
+if(isset($_GET['err']) && $_GET['err'] == 1) {
+echo "<br /><hr /><br /><div class=\"headline\"><span class=\"f10 c5\">Existing Oasis data found in the database! Please clear the 'odata' table before continuing.</span></div><br /><br />";
+}
+
 ?>
 <form action="include/oasis.php" method="post" id="dataform">
 <p>
diff --git a/todo.txt b/todo.txt
index 6847cca8..97399541 100644
--- a/todo.txt
+++ b/todo.txt
@@ -1,6 +1,3 @@
-- cannot delete a single medal in admin
-- add back buttons to Admin where there are not (like editing a user)
-- disallow installation if existing data are in place, or world map would end up screwed and villages not showing (because there can be multiple villages/oasis generated for one square then) 
 - quest image should glow red when new task is ready to be read (now it's only red when page is refreshed)
 - check aliance invitation accepting - apparently it doesn't work too well on first try?
 - normalize forum tables - varchar is used for numeric values and is joined with int field
@@ -10,4 +7,5 @@
 - should random attacks from Natars when building Wonder of the World be unit-less?
 - send forum replies in a forum where a user is active also to that user's mailbox
 - make an option for admin to be raidable (in profile?)
+- finish parts in Admin that are unfinished (mostly delete -X- buttons and Alliance settings)
 - add PayPal listener to verify gold transactions imediatelly
\ No newline at end of file