WinXP SP3.
I cd'd to the \build directory
And then typed ant to run it.
Also tried ant.bat and ant.cmd
Re-entered the set path statements, to point to the ant directory.
I also tried c:\ant\bin\ant to run it.
----------------------------EDIT
I think it ran, I used c:\ant\bin\ant.bat to get it to run
Now just to find the files it made.