I have not used this with a Vista machine, but it has worked for XP machines. While connected by VPN, go to tools, account settings in outlook, click change, click more settings. Click the connection tab. Change to “connect using Internet Explorer’s or a 3rd party dialer”. Then go to the security tab and change network security to “Password Authentication NTLM”. You may have to cancel out of several authentication screens in the process. Just keep clicking cancel and then click ok to close this window. Click next and finish. Hope it works!