[Resolution]Your search cannot be completed because this site is not assigned to an indexer

Error Message:
Your search cannot be completed because this site is not assigned to an indexer. Contact your administrator for more information.

Resolution:
SharePoint 3.0 Central Administration > Application Management > SharePoint Web Application Management: Content databases > [select the content database used by your site] > Search Server: Select Windows SharePoint Services search server

You don't need to configure this manually if you installed Windows Sharepoint Services 3.0 in standalone mode.

Refer to:
http://geekswithblogs.net/JayKinker/archive/2007/09/12/115299.aspx
http://biztalkdev.com/blogs/paulwu/archive/2007/03/22/SharePoint-Error-Your-search-cannot-be-completed-because-this-site-is-not-assigned-to-an-indexer.aspx