I seem to recall that Octave 3.8 Windows binaries/installers used to be available from the main repository before (
https://ftp.acc.umu.se/mirror/gnu.org/gnu/octave/windows/), but now I can't seem to find any versions earlier than 4.0.0. Maybe I'm misremembering or have they possibly been removed or moved somewhere else? It would be nice if they were still accessible somewhere.