You can use the following registry settings in order to configure a Windows machine to automatically log into a domain. This should only be done with low risk/low security computers/users as the password is stored in the clear in the registry.

In the following registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

Create or modify these values:

DefaultUserName
String Value (REG_SZ)
(username to login with)

DefaultPassword
String Value (REG_SZ)
(password to login with)

DefaultDomainName
String Value (REG_SZ)
(domain to log in to)

AutoAdminLogon
Value: 1

If the AutoLogonCount or AutoLogonChecked keys exist, delete them.