How to get the active directory out

I currently have a program in the PC. I want to be able to take in the username and password when he login to the PC and check if he is able to access my program. Only administrator is able to access it so I want to prevent people with user domain from running my program.

How can I do it.
Please provide some sample codes if possible.
Thanks

Public Declare Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA" (ByVal lpBuffer As String, nSize As Long) As Long

retVal = GetuserName(uName, 255)

if nName= "Admin" then do your thing

actually, I want to get the domain too but do not know the code. Please help.

You say that you want to "prevent people with user domain from
running my program." if you mean users that are in the Domain
Users group then I'm not sure, but if you mean that you just
want to get the available domains then try my code in this thread.

And in addition, I have put a login page at my program.This is because in case my administrator is careless and forget to logout of the window, and a user try to use the program. I want to stop the user from accessing the program. This program is suppose to be usable my administrator only.The domain in the window which I want to use to compare if the person using the program is from the admin domain.

Thanks

Then you are talking about detecting the user anme and what
group it is a member of.

If you search the forums you usually can find an answer.
Try this thread.