failed changeDB from SDPlus default install to an external database?

hi,

is it possible to changeDB from default install of service desk plus to an external database?

heres the error:

[root@storage2 bin]# ./startDB.sh
Running stand alone DB server
DB_HOME /opt/ManageEngine/ServiceDesk/bin/../mysql DB_PORT 33366 TMP_HOME /opt/ManageEngine/ServiceDesk/bin/../mysql/tmp
120105 17:33:52 [ERROR] Can't start server: Bind on TCP/IP port: Address already in use
120105 17:33:52 [ERROR] Do you already have another mysqld server running on port: 33366 ?
120105 17:33:52 [ERROR] Aborting

120105 17:33:52 [Note] /opt/ManageEngine/ServiceDesk/bin/../mysql/bin/mysqld: Shutdown complete

running mysql-5.1.47-4.el6.x86_64 as an external database on port 33366 on rhel6 enterprise
also tried to used 3306 for the external db but still unsuccessful

What are the possible cause of this.
I stop the default DB using the stopdb script but seems the startdb script is still pulling the default DB eventhough i change the DB to external.

Any help and suggestions is much appreciated.

thanks