In Windows / Powershell
just create a text file, for example called "xerces.ps1", and put
it inside the Xerces directory you downloaded (where the JARs are).

The file should contain the following two lines:

  $env:CLASSPATH="resolver.jar;serializer.jar;xercesImpl.jar;xercesSamples.jar;xml-apis.jar"
  java $args

From the Xerces directory then you can run

  .\xerces.ps1 dom.Counter telegram.xml

etc...

Please note that you might need to enable script execution
( http://www.windowsecurity.com/articles/PowerShell-Security.html )

Bonus question: can you write a loop to find all JAR files (as
I did for the Bourne Shell)?

-- Chris