Windows vista come with paranoid security, most of network tools are restricted by default. One of the tools is sharing data over the network. While you are trying mapping drive on your machine vista will not granted this connection.
But you can modify the registry in order to allow network sharing data.
- Type regedit on your command line
- Go to HKLM-System-CurrentControlSet-Control-Lsa
- double click LmCompatibilityLevel and set value into 0
Now you can test you mapping drive.