How to fuse Nodeprofile with Drupal's user page

..that function does not exist, he probably meant node_load().

Try this: put the following code in your template.php. I'm assuming you're using CCK to make your nodeprofile. In the code, change 'your_profile_type' into the name of the content type you're using. And replace the part after 'field_' in the string 'field_your_profile_field' into the name of the CCK field that you are using for the user's full name. So if that field is called 'fullname', than you would substitute 'field_your_profile_field' by 'field_fullname'.

/**
 * @param $object
 *   The user object to format, usually returned from user_load().
 *   But can also be a node!
 * @return
 *   A string containing an HTML link to the user nodeprofile
 */
function phptemplate_username($object) {
  // *** Replace username of user everywhere with user's full name.
  // Make links to users always to user nodeprofile instead of userpages, 
  // if exists, and supply appropriate link_text.
  // From template.php in usernode.module.
  if (!empty($object->uid)) {
    // Load nodeprofile
    $nodeprofile = node_load(array('type' => 'your_profile_type', 'uid' => $object->uid)));
    if ($nodeprofile) {
      // Get realname of user.
      $name = $nodeprofile->field_your_profile_field[0]['value'];
      $link = 'node/'. $nodeprofile->nid;
      $link_text = 'Go to the nodeprofile of this user.';
    }
    else {
      // Nodeprofile does not exist.
      $name = $object->name;
      $link = 'user/'. $object->uid;
      $link_text = 'Go to the userpage of this user.';
    }
    if (user_access('access content')){
      $output = l($name, $link, array('title' => $link_text));
    }
    else {
      $output = check_plain($name);
    }
  }
  else if (!empty($object->name)) {
    // Sometimes modules display content composed by people who are
    // not registered members of the site (e.g. mailing list or news
    // aggregator modules). This clause enables modules to display
    // the true author of the content.
    if ($object->homepage) {
      $output = l($object->name, $object->homepage);
    }
    else {
      $output = check_plain($object->name);
    }

    $output .= ' ('. t('not verified') .')';
    return $output;
  }
  else {
    $output = variable_get('anonymous', 'Anonymous');
    return $output;
  }
}

Let me know if this works.