Xerces has been bundled with the JDK since (1.4?). There's no need to download and include its JAR's in project that uses a current version of the JDK. This covers you for SAX, DOM and JAXP, though you will need to download the JDOM JAR's and include them in your classpath.
On a side note, consider using Maven to manage your dependencies, it trivializes the task.