This version of pst-tree uses the xkeyval package, the extended version of keyval. Save the files pst-tree.sty|.tex| in a directory, which is part of your local TeX tree. Then do not forget to run texhash to update this tree if these packages are new to your TeX distribution. pst-tree needs pstricks, which should be part of your local TeX installation, otherwise get it from a CTAN server, f.ex. https://mirror.ctan.org/ hvoss@tug.org