Create a reg file based on your needs. Perhaps autologon.reg and defaultlog.reg
Cut-n-Paste the portion you need from below and save it as a .reg file.
To launch it do something like this;
(assuming it is at the drives root).
REGEDIT /S %systemdrive%\install\autologon.reg
Key values;
"AutoAdminLogon"="1" (allows it to try and logon the default user. =0 means it won't)
"DefaultDomainName"="Your-DOMAIN" (Domain if applicable).
The rest is pretty straight forward.
Then send a modified version to clear the password and values (Just put the end "" togather like this for all the keys except "AutoAdminLogon"="0");
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
"DefaultPassword"=""
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
"AutoAdminLogon"="1"
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
"DefaultDomainName"="Your-DOMAIN"
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
"DefaultUserName"="UserName"
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
"DefaultPassword"="Password"