Installation errors and php configuration

i am trying to access my webpage and are getting these errors

Warning: ini_set() [function.ini-set]: A session is active. You cannot change the session module's ini settings at this time. in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\sites\default\settings.php on line 144

Warning: ini_set() [function.ini-set]: A session is active. You cannot change the session module's ini settings at this time. in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\sites\default\settings.php on line 146

Notice: A session had already been started - ignoring session_start() in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\includes\bootstrap.inc on line 1031

warning: array_fill() [function.array-fill]: Number of elements must be positive in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\includes\database.inc on line 241.
warning: implode() [function.implode]: Bad arguments. in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\includes\database.inc on line 241.
warning: array_keys() [function.array-keys]: The first argument should be an array in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\modules\user\user.module on line 502.
user warning: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 1 query: SELECT p.perm FROM role r INNER JOIN permission p ON p.rid = r.rid WHERE r.rid IN () in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\modules\user\user.module on line 502.
warning: array_keys() [function.array-keys]: The first argument should be an array in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\modules\block\block.module on line 406.
warning: array_fill() [function.array-fill]: Number of elements must be positive in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\includes\database.inc on line 241.
warning: implode() [function.implode]: Bad arguments. in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\includes\database.inc on line 241.
warning: array_merge() [function.array-merge]: Argument #2 is not an array in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\modules\block\block.module on line 407.
user warning: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') OR r.rid IS NULL) ORDER BY b.region, b.weight, b.module' at line 1 query: SELECT DISTINCT b.* FROM blocks b LEFT JOIN blocks_roles r ON b.module = r.module AND b.delta = r.delta WHERE b.theme = '' AND b.status = 1 AND (r.rid IN () OR r.rid IS NULL) ORDER BY b.region, b.weight, b.module in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\drupal-6.12\drupal-6.12\modules\block\block.module on line 407.

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how do i get this resolved