I had been trying for some time to create a mapped network drive to a remote WebDAV folder using Vista, but I was unable to figure this process out until recently. Apparently, Microsoft has a Software Update for Web Folders (KB907306) that enables the Web Folders component in Vista. Once the update is installed, you should be able to map your drive.

1. Open the Computer icon on the desktop or Start menu
2. Select "Map Network Drive" in the top toolbar
3. Select "Connect to a Web site that you can use to store your documents and pictures" 
   
   
    
4. Select "Choose a custom location"
   
   
   
5. Enter the URL of the folder you want to connect to (i.e. https://www.myserver.com/myfolder/)
6. Follow the steps outlined in the Wizard, they should be pretty self-explanatory.