You can use the following to make the user name and domain field for the Windows XP login screen default to a pre-defined value after you’ve deployed an operating system. This is handy because sometimes after the task sequence has finished and it reboots and leaves the PC at the Windows login screen, the default domain to login to is the local workstation instead of your domain.
You can set these values a couple different ways during your task sequence. You can use a Powershell script, a vbscript, or import a registry key. Below are examples of a reg file you could import and a Powershell script you can run. I would only go the Powershell route if your already running a couple of Powershell scripts and can include this one with the others all in the same script.
Windows Registry Editor Version 5.00
$winlogon = “registry::HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogon”
set-itemproperty $winlogon -name “DefaultDomainName” -value “domain_name”
set-itemproperty $winlogon -name “DefaultUsername” -value “Username”