asant Build Failing

I'm trying to build the source on a windows vista installation. I've followed all the instructions for installing the Java SDK and I am getting this build error. I think I have a classpath wrong or something. The compiler does not know where to find javax.media.j3d and I am not sure where to tell it to look.

[echo] Reprap: C:\Users\David Powell\Software\RepRap\reprap-host-src-0.8.1\reprap-host-src-0.8.1\build.xml
[javac] Compiling 72 source files to C:\Users\David Powell\Software\RepRap\reprap-host-src-0.8.1\reprap-host-src-0.8.1\bin
[javac] C:\Users\David Powell\Software\RepRap\reprap-host-src-0.8.1\reprap-host-src-0.8.1\src\org\reprap\Printer.java:5: package javax.media.j3d does not exist
[javac] import javax.media.j3d.*;

Never mind. I figured it out. I had to manually install the j3d and rxtx packages because they were being installed into the wrong folders for some reason. It wanted to install them in C:\Program Files\Java\... and I needed them in C:\Sun\... I'm not really sure how I ended up with two different install folders. Maybe somone here can shed some light on the subject.

Am I supposed to be using the C:\Program Files\Java... installation as my JDK? I simply installed the latest JDK in the default directories on Windows Vista and ended up with two different directories. C:\Sun was automatically added to my Environment variables which is why I am using that one. I guess I could add an environment variable to the other instead since all the documentation refers to that directory. Whats the deal?