[Typo3] turn off ldap authentication behind the scene?

[Bing Du]

I installed ldap_lib, ldap_auth and ldap_server and did some 
configurations (ldap server, protocol, basedn, etc.).  LDAP 
authentication was enabled for both FE and BE.  Then I logged out as 
admin.  Now I'm not able to log back on as admin on BE again.  Where 
does typo3 store ldap configurations, in file or db?  Is there any way 
to turn ldap authentication off without using BE?

Thanks in advance for any help.

Bing