the core search feature needs a search results module installed on a page named search results. Apparently someone removed that page and the module from your installation.... not a very easy thing to put it back as it is a core module that does not have an inst

you can put the files back from a dnn install zip of the same version. Look for the folder /admin/search

Next you need to reregister the module, which can be done by running the following scriptsfrom host>sql (please check "Run As Script"):

-- start script

DECLARE @DesktopModuleID INT
DECLARE @ModuleDefID INT
DECLARE @ModuleName NVARCHAR(50)
SELECT @ModuleName = 'Search Results'
INSERT INTO {databaseOwner}[{objectQualifier}DesktopModules]([FriendlyName],[Description] ,[Version] ,[IsPremium] ,[IsAdmin] ,[FolderName],[ModuleName],[SupportedFeatures] ) VALUES (@ModuleName,'The Search Reasults module provides the ability to display search results.' ,'01.00.00' ,0,0 ,@ModuleName ,@ModuleName ,0 )
SELECT @DesktopModuleID = SCOPE_IDENTITY()
INSERT INTO {databaseOwner}[{objectQualifier}ModuleDefinitions]([FriendlyName],[DesktopModuleID],[DefaultCacheTime]) VALUES (@ModuleName,@DesktopModuleID,-1)
SELECT @ModuleDefID = SCOPE_IDENTITY()
INSERT INTO {databaseOwner}[{objectQualifier}ModuleControls] ([ModuleDefID] ,[ControlSrc] ,[ControlType] ,[ViewOrder] ,[SupportsPartialRendering]) VALUES (@ModuleDefID ,'Admin/Search/SearchResults.ascx' ,-1 ,0 ,0)

-- end script

the search module is now available in your portal. All you need to do is to create a page that will contain the Search Results module. this page does not have to appear in your menu, but it must be an active page, and accessible for nonauthenticated users