The default download installation of Jboss 4.0.4 AS has xerces under C:\jboss\lib\endorsed. I am using JDK 1.5 as JRE runtime which already includes JAXP 1.3 and xerces implementation as part of core java package. So will there be a clash between xerces in endorsed dir of jboss and jdk1.5? If so which implementation will be used? So should I removing xerces from endorsed dir if there is a clash?