By default Windows Vista won't authenticate Samba share folders. Here is the quick fix you'll need to do to get the two to talk.
Early adopters of Microsoft’s new Vista operating system may notice that it will not connect to Samba share folders out of the box. This will be a bit of a pain for many enterprise customers. The technical reason is because Microsoft Vista’s default security policy is to only use NTLMv2 authentication. According to a Google search Samba doesn’t support this yet.
Update: Some readers have pointed out that NTLMv2 authentication is supported in Samba 3.0. However, this certainly wasn't an option to get this running in my instance.
To get Vista to work with Samba follow the simple instructions below:
1. Open the Run command and type "secpol.msc".
2. Press "continue" when prompted by Vista.
3. Click on "Local Policies" --> "Security Options"
4. Navigate to the policy "Network Security: LAN Manager authentication level" and open it.
5. By default Windows Vista sets the policy to "NTVLM2 responses only". Change this to "LM and NTLM – use NTLMV2 session security if negotiated".
Once you’ve done this Windows Vista will be able to view network drives based on Samba servers and should fix any issues around using Samba as a Primary Domain Controller.