To get the current logged in user at the system I use this code:
string opl = System.Security.Principal.WindowsIdentity.GetCurrent().Name.ToString();
If you're using membership you can do: Membership.GetUser()
Membership.GetUser()
Your code is returning the Windows account which is assigned with ASP.NET.
Additional Info Edit: You will want to include System.Web.Security
using System.Web.Security