Something to bear in mind is that System.Environment.MachineName;
and System.Windows.Forms.SystemInformation.ComputerName;
will give you the NETBIOS name of the machine (restricted to 15 characters).
If you want the full TCP/IP based host name you can use Dns.GetHostName():
string hostName = System.Net.Dns.GetHostName();
Or you can use:
System.Environment.GetEnvironmentVariable("COMPUTERNAME");
Which will return the full computer name set during installation.