This article details the search options available in WSS-only sites.
Searching in WSS is simple and doesn’t have many options; every site
(usually) has a search box that enables you to search on documents and
list items in that site.
Next
to the search box is a scopes drop-down that enables you to choose from
scopes if any are configured. By default, you only have the choice of
searching the site itself (see Figure 1).
When you are viewing a document library, the search box has an additional option in the scopes drop-down (see Figure 2). This option enables you to search only within the document library, excluding other document libraries.