For windows XP:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
"DefaultUserName"="NOD32"
For Windows 7:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\LogonUI]
"LastLoggedOnSAMUser"="domain\\username"
"LastLoggedOnUser"="domain\\username"
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\SessionData\1]
"LoggedOnSAMUser"="domain\\username"
"LoggedOnUsername"="domain\\username"
