hi there,
i had the same problem and the solution was so easy, that i didn't see it.
first of all you have to copy your php.ini into your system folder (c:\winnt) (i've deletet the php.ini from c:\php not to get confused ...).
still had trouble, so i set the path environment variable to
c:/php/dlls
(try not to include and require the ldap dll :-)
hope that helps,
mike
p.s.: reboot after changes !