If you are using ActiveState perl instead, you may want to try a pre compiled PPM instead. First use "perl -v" to find out which version you are running.

For perl 5.8.*:

C:\> ppm
ppm> set repository theoryx http://theoryx5.uwinnipeg.ca/ppms/
ppm> install XML-LibXML
[download]

For perl 5.10.*:

C:\> ppm
ppm> set repository theoryx http://cpan.uwinnipeg.ca/PPMPackages/10xx/
ppm> install XML-LibXML
[download]