What did I do wrong?

Hi

When I go to my new Drupal site I get this:

Notice: Undefined variable: conf in C:drupalincludescommon.inc on line 776

Warning: Cannot send session cookie - headers already sent by (output started at C:drupalincludescommon.inc:776) in C:drupalmodulesuser.module on line 5

Warning: Cannot send session cache limiter - headers already sent (output started at C:drupalincludescommon.inc:776) in C:drupalmodulesuser.module on line 5

Notice: argument passed to unserialize() is not an string in C:drupalmodulesuser.module on line 80

What do I do about it?

/Roger