I see this question being asked a lot in the forums so decided to make it an add-on.

This simple add-on enhances your quick search box to search for the keyword in product description and all categories including subcategories.

open catalog/includes/boxes/search.php

FIND:

'text' => tep_draw_input_field('keywords', '', 'size="10" maxlength="30" style="width: ' . (BOX_WIDTH-30) . 'px"') . ' ' . tep_hide_session_id() . tep_image_submit('button_quick_find.gif', BOX_HEADING_SEARCH) . '
' . BOX_SEARCH_TEXT . '
' . BOX_SEARCH_ADVANCED_SEARCH . '');

REPLACE WITH:

'text' => tep_draw_input_field('keywords', '', 'size="10" maxlength="30" style="width: ' . (BOX_WIDTH-30) . 'px"') . ' ' . tep_draw_hidden_field('search_in_description', '1') . tep_draw_hidden_field('inc_subcat', '1') . tep_hide_session_id() . tep_image_submit('button_quick_find.gif', BOX_HEADING_SEARCH) . '
' . BOX_SEARCH_TEXT . '
' . BOX_SEARCH_ADVANCED_SEARCH . '');

That's it.
nimz

ps: only new shop installation can over write the included catalog/includes/boxes/search.php file

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