If having Network Neighborhood installed then it might request for login, but it can be disabled:
- Open Control Panel and double click the Network-applet
- Select the Configuration-tab
- change the dropdown Primary Network Logon from Client for Microsoft Network to Windows Logon
More info MS KB152104
[HKEY_LOCAL_MACHINE \Software \Microsoft \Windows \CurrentVersion \Winlogon]
AutoAdminLogon = "1"
DefaultUsername = "username"
DefaultPassword = "password"
Note requires that username of the previous user is NOT cleared.