Reasons for an SSP administrator to do a full crawl include:
Note:
The crawler cannot discover when ASPX pages on Windows SharePoint Services 3.0 or Office SharePoint Server 2007 sites have changed. Because of this, incremental crawls do not re-index views or home pages when individual list items are deleted. We recommend that you periodically do full crawls of sites that contain ASPX files to ensure that these pages are re-indexed.
The system does a full crawl even when an incremental crawl is requested under the following circumstances: