This will allow you to search by the sku in the search box on the home page, it seems pretty stupid that this is not enabled anyways in xcart.
In search.php
Add:
Anywhere between "substring", and "manufacturers");
Code:
$allowable_search_fields = array (
"substring",
......................
"manufacturers");
In skin1/customer/search.tpl
Add:
Code:
<input type="hidden" name="posted_data[by_sku]" value="Y" />
after
Code:
<input type="hidden" name="posted_data[by_fulldescr]" value="Y" />
In skin1/customer/main/search_result.tpl
Add:
Code:
searchform_def[9] = new Array('posted_data[by_sku]', true);
after:
Code:
searchform_def[8] = new Array('posted_data[weight_min]', '{$zero}');