Mapper.xml is actually not an .xml file, it's actually a Perl (.pl) file. You cannot open it with your web browser at all. No part of this process uses the web browser.
You need to run it from a command prompt. To get to a command prompt, go to Start->Run and enter "cmd". That will open a command prompt. You then need to CD to where ever you have the mapper.xml file stored.
At the prompt:
C:\Documents and Settings\your_name\ > cd \my_maps\
c:\my_maps\ > perl mapper.xml logfile_to_parse.txt > output_file.svg
That will run the perl script, mapper.xml, taking the logfile you give it and dumping the results in the .svg file. You can then open the .svg file in Inkscape (or another SVG editor)
BTW, you may want to use my version of Mapper, Mapper2. It is a little more user friendly and has some more options.
Download it here:
http://www.eq2interface.com/download...fo.php?id=3936
Note also that there is a batch file - the Batch file can be setup to do the parse and automatically launch the SVG editor.