need help with ANT!!!!!

Hi,
I am using Ant thru eclipse IDE,
wheni runthe build script it gives me the following error

BUILD FAILED:
com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK
Total time: 1 second

the problem is i have the JRE, and i have set the path as follows

Java_Home = C:\Program Files\java\j2re1.4.2_01\bin
classpath = C:\Program Files\java\j2re1.4.2_01\bin;
Path = C:\Program Files\Java\j2re1.4.2_01\bin;

and i run ant fromthe command prompt it even gives me this error saying "tools.jar not found!"

i have a JRE, do ineed to get the JDK , if so which one and cani install it in the same folder c:\programfiles\java
where the JRE is ;located? or should i store it somehweere different!

please i need help urgetnly!!!1

maybe install myEclipse plugin.. myeclipseide.com
and jdk

i dont think it is the eclipse part
i think maybe it is that i need a jdk not just the jre

i amnot sure
i am a novice to this too so need help!!