the above link (php-5.3.5-Win32-VC6-x86.zip) is dead. can not find the 5.3.5 zip for vc6. thus i got "PHP Warning: PHP Startup: ldap: Unable to initialize module".
Edit: Finally, I used the php_ldap.dll contained in the 5.3.4: http://windows.php.net/downloads/releases/archives/php-5.3.4-Win32-VC6-x86.zip and seems to work for now.
php: php-5.3.5-Win32-VC6-x86.msi, apache: httpd-2.2.17-win32-x86-no_ssl.msi, windows: win 7 (64 bit)
Thanks, and sorry to have bother you.