Microsoft full-text search is an umbrella technology. Different products (like SharePoint Portal 2003, Exchange and SQL Server) use variants of this technology. Here is a brief look at full text search capability of WSS V2 vs WSS V3/MOSS 2007 and how full text search is done in these three products:
WSS V2 (SharePoint Portal 2003): You can enable all your content databases to be indexd by SQL Full-Text searh.
1) Make sure that Full-Text Search subcomponent is installed on your SQL Server 2000 Instance. As I said before, SharePoint relies on SQL Server Full-Text Search capabilities for an efficient retrieval of unstructured, textual data by means of a full-text index.
2) Make sure that MSSearch service is setup and marked to auto-start and run under the LocalSystem account.
3) You must upgrade your SQL Server 2000 to use Service Pack 3a
4) Click Start, point to Administrative Tools, and then click SharePoint Central Administration to connect to Windows SharePoint Service Central Administration.
5) In the Component Configuration area, click Configure full-text search.
6) Click to select the Enable full-text search and index component check box, and then click OK
WSS V3: SQL Full text search no longer works with this version .WSS 3.0 search is a subset of MOSS 2007 search with search restricted only to the same site (or if you are in a list to the same site And list).
I) You need to have the WSS Search service started start >>Administrative Tools >> WSS 3.0 Central Administration >>OperationsàServices on Server – by default it is started.
II) When you create web applications you must select a search server.
III) If you add a content database you must select a search server.
MOSS 2007: Enterprise search framework in MOSS 2007 has been completely changed and is a “Microsoft Office SharePoint Server 2007 Shared Service” (Remember, bunch of these expensive services like search will form a SSP or Shared Services Provider). This service supports full-text, keyword searches and IFilter.