[otrs] Configuring System Auth LDAP after install

Hi, I installed OTRS a couple of weeks ago using it's internal MySQL authentication. I've just been asked to change this to use the Windows 2003 AD server (via LDAP I assume). I currently only have two user accounts (other than root@localhost) in OTRS. I've looked through OTRS documents but can't really find how to now change from the MySQL auth to LDAP auth. I also don't want to re-install OTRS. Can someone point me in the right direction for where I can find howto's or wiki information about how to "convert" from mysql auth to Windows AD auth (via LDAP). Thanks. Michael.