X-Commands is an application that you need to have on your drive to run scripts that are calling for it. If you downloaded the package you should have the application.
FYI : X-Commands is an older version of David LLoyd’s software, the latest version is named Extra Suites, go to http://www.kanzu.com/ and download the package. It has several sample scripts that will help you out.
“X-Commands PPC” was the old name for Extra Suites. Either change the name in your script from “X-Commands PPC” to “Extra Suites” or, when it asks you to locate “X-Commands PPC” simply choose Extra Suites from the list of applications.