Windows Vista / Windows 2003 and WebDAV over HTTP (not S)

There's a good article about the problem to do a WebDAV connection without SSL on Vista / Win2003:

SharePint, WebDAV, and http (not https)

Here's the abstract:

1. Fire up regedit.exe (if UAC is enabled you'll have to approve it of course)
2. Navigate to the key HKEY_LOCAL_MACHINE\
   SYSTEM\CurrentControlSet\Services\WebClient\Parameters
3. Change the setting BasicAuthLevel from its current value (default 1) to 2 (0 means disabled, 1 is https only, 2 is both http and https)
4. Enter the following commands:
   1. net stop webclient
   2. net start webclient
   3. net use x: "http://yoursharepointprovider.tld/somesharename" /user:"whateverdomain\yourusername" /persistent:yes
   4. Enter your password when prompted

Update:

For Windows 2003 server the DWORD value you must add to the registry under the Parameters key above is UseBasicAuth and set its value to 1 and you'll also want to update the AcceptOfficeAndTahoeServers key from 0 to 1.  You cannot just net stop/start webclient; instead you must net stop mrxdav then net start webclient.  I found this out from KB841215.