How to reset authorization settings of QC

Can any one help to reset the Authentication settings of Mercury Quality centre.
I logged in as administrator and chose authentication option as LDAP and did not import any user list.
I tried to re login to QC but login has failed due following error.

Failed to Login;
Failed while trying to locate user in LDAP server (missing LDAP import settings). Please contact the site administrator to resolve the problem.;
Application Parameter 'DIRECTORY_PROVIDER_IMPORT_URL' does not exist;

Now I am not in a position to revert the LDAP Authentication setting.
It will be great if any one can help on this.
Environment: windows XP and Mercury Quality centre 9.0

Change authenitication from LDAP to Quality Center from the database schema

Note:
If you cannot access the database schema, please contact your Database Administrator.

1. Access qcsiteadmin_db schema.
2. Select the PARAMS table.
3. Change the PARAM_VALUE from "LDAP" to "QualityCenter" for the PARAM_NAME "AUTHENTICATION."
4. Restart the Quality Center service or the server machine.