When processing large amounts of data, PSPP placed a temporary directory on the root of the homedir with names like pspp<something-random> and left them there.
For example c:\psppz6yaq9k.
You don't need them and can delete these directories after PSPPIRE is closed.
This build uses a MSWindows syscall to find the place where temporary files have to be stored. This looks the cleanest way possible but has to be tested on networks etc.
See http://git.savannah.gnu.org/gitweb/?p=pspp.git for the updates in PSPP itself.