FYI - to help others out -

I disabled the WebDAV service based upon the information from
www.blackviper.comThen, I struggled with some Sharepoint functionality I wanted.
The WebClient service is used with SharePoint 2007 (3.0) for sure - maybe 2.0 also. I'm using a Vista computer to access the SharePoint server, but XP SP2 also seems to be affected.
The WebClient service is used so you can easily save from Excel, Word, etc directly to the SharePoint site.
I don't know the exact technicalities, but it communicates via WebDAV to the SharePoint server, and basically allows you to browse the SharePoint Document Centers as if they were folders on a network share (e.g. using \\servername\Docs\Company Info)
This website from MS has more information about making sure WebDAV works properly with HTTP and HTTPS and it was how I discovered that WebDAV was the communication link between my computer and the SharePoint server.
http://support.microsoft.com/kb/841215Cheers -