I installed 5.3.3 today on a Windows server. LDAP is no longer in the ext directory but listed in the php.ini ... just one of many. It exists in the VC9 builds though.
I'm finding more and more of the binary dlls are no longer being bundled in the thread-safe Windows downloads and PHP users are being asked to compile it themselves.
You will need to get and compile LDAP client libraries from either » OpenLDAP or » Bind9.net in order to compile PHP with LDAP support.