using System.Management;
SelectQuery query = new SelectQuery("Win32_UserAccount");
ManagementObjectSearcher searcher = new ManagementObjectSearcher(query);
foreach (ManagementObject envVar in searcher.Get())
{
Console.WriteLine("Username : {0}", envVar["Name"]);
}
This code is the same as the link KeithS posted. I used it a couple years ago without issue but had forgotten where it came from, thanks Keith.