Troubleshooting network authentication problems in Vista

Because Microsoft decided to enable NTLMv2 by default in Vista, it is very likely that you have received Authentication Error when you were trying to connect to older machines which don’t have NTLMv2 enabled (Windows XP, Windows 2000 and some older versions of Windows have NTLMv1 enabled by default).

These three .reg files might help you to solve the problem:

• Send LM and NTLM Responses (send NTLMv2 when negotiated) – recommended
• Send LM and NTLM Responses
• To restore the default Vista setting, use this file: Send NTLMv2 only

Don’t forget to restart your computer once the reg file is merged into the registry. Note: If you have Vista Business or Vista Ultimate, you can also use Start -> Run -> secpol.msc and under Local Policies -> Security Options look for Network security: LAN Manager authenication level.