There's a "Site Collection Search Results Page" field which is used for configuring the search results page used for contextual searches (such as "This Site"). It can be found by doing the following:
- Go to your SharePoint site collection
- Select "Site Settings" from the "Site Actions" menu
- Go to the "Site Collection Administration" section and select "Search Settings"
- The field "Site Collection Search Results Page" will be listed on the bottom.
The default value is
/_layouts/osssearchresults.aspx
How can I retrieve and change this value through the SharePoint object model?