No you can not modify it with KiXtart. It is called GINA, Graphical Identification and Authentication

There are many posts on the Web about modifying this, and Microsoft has a recent one located here.

NOTE: from the author of the article.
Quote:

Let me state up front that replacing the GINA is an advanced technique that should not be taken lightly. You should only do this if you have no other choice (if, for example, you are implementing a new logon mechanism that Windows does not support).




Customizing GINA, Part 1