how map drive-letter to webDav drive (XP/SP2)

I have successfully set up one of the directories of my website to be a webDAV drive. So for so good. Using the "guide to setting up WebDav with Windows XP on the Dreamhost wiki" http://wiki.dreamhost.com/index.php/KB_/_Account_Control_Panel_/_Goodies_::_Htaccess_/_WebDAV_/_WebDAV#Setting_up_WebDAV_on_Windows_2000_or_Windows_XP

Then I set successfully up this directory as a Network Place under Windows XP SP2. Whoopy.

What I really want ("need" actually) is to assign a drive-letter (X: or whatever) to this directory.

Have tried the following Net Use command:

net use x: "http://www.mydomain.com/WEBDAV" /User:username password /persistent:yes

This returns the following error message: System error 5 has occurred. Access is denied.

If I use this script:

net use x: "http://www.mydomain.com/WEBDAV:80" /User:username password /persistent:yes

I get the following error mesages:

System error 67 has occurred. The network name cannot be found.

Where did I go wrong (and more importantly: what is correct way to do this)???

Thanks for any help & insights!