Solved my own problem. After many hours of checking everything I could, as deep as I could go, it was something simple. The other program had turned off the Welcome Screen. I didn't even know it was an option under User Accounts...Duh. Everything works fine now.
Logon studio creates the correct logonuiX file and correctly switches in the registry between this and logonui.exe but the file does not run. The login screen that comes up since I tried one of your competitors (now uninstalled) is one I have never seen before but looks like a genuine Windows login of some type. This is an XP Home system. I used Logon Studio to look in logonui.exe and it has the correct graphics in it for the original XP login screen.
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