WSS V3提供了独立于IIS6.0的WebDAV 服务
Many people are under the misconception that SharePoint uses the WebDAV functionality provided by IIS 6.0. Actually, SharePoint provides its own WebDAV implementation using the Stsfilt.dll ISAPI filter that is installed with both Windows SharePoint Services and SharePoint Portal Server. Enabling or disabling the WebDAV extension in IIS 6.0 has no effect on SharePoint functionality.
具体可以查看一下文档 http://www.microsoft.com/downloads/details.aspx?FamilyID=C523AC7A-5724-48BE-B973-641E805588F4&displaylang=en