Restrict Drupal Search to few content types
I guess that Custom Search module can help you: http://drupal.org/project/custom_search. acording Custom Search module description:


  The module adds options to select:

* which content type(s) to search



here a snapshot of Custom Search settings related with content type configuration:



Other alternative seems to be Search Configuration module http://drupal.org/project/search_config that give to Search settings (in Additional Node Search Configuration > Only of the type(s) settings) options to filter search by content type: