electron,
Bill819 is quite right. Notepad works fine for editing. However when you do your first file save in Notepad it will append the .txt extention onto your file. You may get a file named something like 'Haldata.brn.txt' Just rename the file to remove the .txt or Hal won't be able to use it.
That's fine for .brn files. The Hal brain itself, the .uhp file, is best edited using Hal's built-in brain editor.
=vonsmith=