Let's briefly go through what is kept in each of these directories.

This is the main FrontPage extension installation directory. If you run the fp_install.sh script that you can download with the tarball, it untars the tarball into this directory. Besides having the version directory, it also can contain configuration files for each virtual host on your server. After installing a root web there should be a file named we80.cnf in here that specifies the defaults for virtual servers. You can also create additional config files named domainname:port.cnf in this directory that give more fine grained control over specific virtual domains.

This directory holds the specified version of the extensions.

This directory contains the precompiled stub executable programs that will be installed in a root web or sub web if you use the fpsrvadm.exe program. These executables are statically linked however, so it would be wise to recompile your own fpstub executable by compiling the source code found in the version4.0/srcs directory.