We had this requirement the other day to make "This Site" as default search scope in the search dropdown list on our SharePoint sites.
This setting is configured on a xml file "SearchArea" present in the features folder. Here are the steps to achieve this:
1. Navigate to C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\FEATURES\OSearchEnhancedFeature folder on the front end server(s)
2. Open the file "SearchArea.xml" in notepad
3. Add new property line just above closing control tag with Property Name as "DropDownMode" and value as "ShowDD_DefaultContextual"
4. Save and close the file. Do an IISRESET
Perform the following steps on all the WFE servers in the farm.
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