I'm currently working on a package with the source code of the new Windows installer including the required utilities (modified versions of Aspell, Aiksaurus, Dvipost, DTL, Bakoma fonts etc.). This will make it a lot easier to compile the installer package and create a stable Windows version of LyX.
Are you going to upload sources or patches of aspell etc? It is better to put the installer in the trunk, since a branch sounds temporary to me. Then, we'd better only keep patches to external programs. If the installer works for both 1.4.x and 1.5.x, the top directory (parellel to lyx-devel and www-devel) may make sense. Just my 2c, Lars has the authority. Bo