You need to modify the tomcat-users.xml file in the users' Tomcat base dir,
<userhome>\.netbeans\5.0\jakarta-tomcat-5.5.9_base\conf\tomcat-users.xml
, not the one in IDE installation dir.
C:\Program Files\netbeans-5.0\enterprise2\jakarta-tomcat-5.5.9\conf
e.g. edit this:
C:\Documents and Settings\<user>\.netbeans\5.0\jakarta-tomcat-5.5.9_base\conf\tomcat-users.xml