set JAVA_HOME in windows but "ant build" still fails

I've set JAVA_HOME in my Windows environment preferences:

echo %JAVA_HOME%  
C:\Program Files (x86)\Java\jdk1.6.0_20

However whenever I try to run ant build I get the following:

Perhaps JAVA_HOME does not point to the JDK.
It is currently set to "C:\Program Files\Java\jre6"

I think the registry key JAVASOFT is interfering with my environment variable, but I'm not sure.

Answer

I needed to copy the Tools.jar file from the jdk/lib folder to the jre/lib folder.