One thing you might try is to install the CPAN version of PPM on your machine; to do this, download the PPM-2.1.8.tar.gz source, extract the files, change into the unpacked directory, and run

   perl Makefile.PL
   nmake
   nmake install
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For this, you'll need to install nmake for Windows. After this, you can install XML-LibXML from the uwinnipeg 5.6 repository by issuing the command

ppm install http://theoryx5.uwinnipeg.ca/ppmpackages/XML-LibXML.ppd
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This should also install the prerequisite ppm packages, as well as the required libxml2.dll library (which goes somewhere in your PATH).