Domain is coming back appended to username for : Context.User.Identity.Name

Hello,
I have a perplexing problem. I have two nearly identical applications. And essentially
the web.config files used for both are also identical. Inside of these web.config
files are my connection strings and they both point to the same database.
What is strange, is that when I trace into the C#/asp.net code for both applications,
one application is coming back with the domain preceding the username, and the other
application is not. For example for the first web application, for the following line
of code:

 Session.Item("txtUsername") = Context.User.Identity.Name
 The value for Context.User.Identity.Name is coming back with simply my username
 "rgoger"
 In the second application the value returned for
 Session.Item("txtUsername") = Context.User.Identity.Name is coming back
 with my username preceded by the domain : "polto-a ...