Adding command button to Windows Logon screen [closed]

Answer 1

For implementation of login/authentification in Windows you may read about GINA,

GINA is a replaceable dynamically linked library that is loaded early in the boot process in the context of Winlogon when the machine is started

Answer 2

That would depend hugely on the OS; pre-vista, GINA; post-vista, LogonUI can be extended by a custom credential provider (as discussed here). However, it won't be easy - and probably risky too.

Answer 3

Modifying login screens is a rather obscure science.

For Windows XP and below, you will need to create a custom GINA (Graphical Identification and Authentication) DLL. This process is described in this MSDN magazine article.

As for Vista and above, you will need to create a custom Credential Provider. It is demonstrated in this MSDN magazine article.

I wouldn't recommend doing what you are doing. This could be a huge security breach.