Kerry,

Try something like this ...

Select 
  AU.Username,
  U.FirstName,
  U.LastName,
  AM.loweredEmail,
  AM.CreateDate,
  AM.LastLoginDate,
from 
  aspnet_Membership as AM with (nolock)
  join aspnet_Users as AU with (nolock) on AM.UserID = AU.UserID
  join Users        as U  with (nolock) on U.UserName = AU.Username
where 
  AM.ApplicationID = (select ApplicationID from dbo.aspnet_Applications where ApplicationName = 'DotNetNuke')

If you are confident that the Application ID will not change then you could hardcode the GUID ...

Hope this helps
Paul