Unable to find a javac compiler

<?xml version="1.0" encoding="UTF-8"?>
<project basedir="." default="build" name="Bienvenue">
  <target name="build">
	  <!-- Creation du dossier classes -->
    <mkdir dir="classes"/>
	
    <!-- Compilation des classes du programme -->
    <javac srcdir="src" destdir="classes" />
        
    <!-- Creation du dossier install -->
    <mkdir dir="install/lib"/>
	
    <!-- Creation du fichier Bienvenue.jar -->
    <jar destfile="install/lib/Bienvenue.jar" basedir="classes"/>
	
    <!-- Suppression du dossier classes -->
    <delete dir="classes"/>
<copy todir="install/jre6">
      <fileset dir="D:\Program Files\Java\jre6">
        <include name="*"/>
        <include name="bin/**"/>
        <include name="lib/**"/>
        <exclude name="lib/charsets.jar"/>
        <exclude name="lib/ext/sunjce_provider.jar"/>
        <exclude name="bin/rmid.exe"/>
        <exclude name="bin/rmiregistry.exe"/>
        <exclude name="bin/tnameserv.exe"/>
        <exclude name="bin/keytool.exe"/>
<exclude name="bin/kinit.exe"/>
        <exclude name="bin/klist.exe"/>
        <exclude name="bin/ktab.exe"/>
        <exclude name="bin/policytool.exe"/>
        <exclude name="bin/orbd.exe"/>
        <exclude name="bin/servertool.exe"/>
        <exclude name="bin/java.exe"/>
        <exclude name="bin/javaws.exe"/>
        <exclude name="bin/javacpl.exe"/>
<exclude name="bin/jucheck.exe"/>
        <exclude name="bin/jusched.exe"/>
        <exclude name="bin/wsdetect.dll"/>
        <exclude name="bin/npjava*.dll"/>
        <exclude name="bin/npoji610.dll"/>
        <exclude name="bin/regutils.dll"/>
        <exclude name="bin/axbridge.dll"/>
        <exclude name="bin/deploy.dll"/>
        <exclude name="bin/jpicom.dll"/>
        <exclude name="bin/javacpl.cpl"/>
        <exclude name="bin/jpiexp.dll"/>
        <exclude name="bin/jpinscp.dll"/>
        <exclude name="bin/jpioji.dll"/>
        <exclude name="bin/jpishare.dll"/>
        <exclude name="lib/deploy.jar"/>
        <exclude name="lib/plugin.jar"/>
        <exclude name="lib/deploy/messages*.properties"/>
        <exclude name="lib/deploy/splash.jpg"/>
      </fileset>
    </copy>
<!-- Creation du fichier Bienvenue.exe avec Launch4j -->
    <exec executable="D:\Program Files\Launch4j\launch4jc.exe">
      <arg value="${basedir}\installerLaunch4j.xml"/>
    </exec>
	
  </target>
</project>

com.sun.tools.javac.Main is not on the classpath. 
Perhaps JAVA_HOME does not point to the JDK. 
It is currently set to "D:\Program Files\Java\jre6"

D:\Program Files\Java\jdk1.6.0_20\bin;D:\Program Files\Java\jdk1.6.0_20\lib;D:\Program Files\Java\jdk1.6.0_20\lib\tools.jar