Windows Authentication in ASP.NET 2.0 question.

I have an active directory domain ABCD.

I have a internal asp.net 2.0 web application located at myApp.myDomain.com.

I am using*
**


My problem is when users navigate to this site it attempts to log them in as

user: myApp.myDomain.com/adUserName
password: adUserPassword.

i need it to attempt to login them in as part of there AD domain such as:

user: ABCD/adUserName
password: adUserPassword.


Any idea what it is i'm missing that causes the application to default to its myApp.myDomain.com instead of the active directory domain?