Downgrade Vista default security to NTLM from NTLM2 to support older RAS server

Click "Start -> Run." Then, type in the Run field: "secpol.msc." That will bring you to Vista's security policy system. Once there, use "Go to: Local Policies > Security Options" and then find "Network Security: LAN Manager" authentication level. Once there, change the Setting from "Send NTLMv2 response only" to "Send LM & NTLM -- use NTLMv2 session security if negotiated."

Other possible fixes:

1. Authentication Protocol Vista does not support the MSCHAPv1 protocol for authentication. The protocols supported on Vista are PAP, CHAP, MSCHAPv2, PEAP and EAP. The default is MSCHAPv2. Hence, if the server is not configured for or does not support any protocol other than MSCHAPv1 then connection setup will fail. Please enable MSCHAPv2 support on the server.

2. Encyption Type Setting Vista supports only strong encryption by default which is 128-bit RC4 for PPTP and AES 128 bit, AES 256 bit, 3DES for L2TP. So, if the server doesnt support these encryption types connections will fail. The solution is to either upgrade the server to support these encryption types or to configure the client to support weaker encryptions types. The latter can be accomplished as follows Change the following registry keys to 1: HKLM\System\CurrentControlSet\Services\Rasman\Parameters\AllowPPTPWeakCrypto FOR PPTP HKLM\System\CurrentControlSet\Services\Rasman\Parameters\AllowL2TPWeakCrypto FOR L2TP

Restart your machine after changing the value of a key