You can also use Resource Hacker to edit the Login screen
Just open
%windir%\System32\LogonUI.exe file in Resource Hacker and do what u want
For more information on Resource Hacker, u can visit following threads:
TUTORIAL: All About Resource Hacker! A Brief Tutorial
TUTORIAL: List of Files to be hacked using Resource Hacker!
And for changing the Text in Login screen, pls read following thread:
TUTORIAL: Changing Windows XP Login Screen Text Entries !