You can use Guid.NewGuid method
public static Guid NewGuid();
Every time you call this method a new Guid
is generated.
Edit: Based on your comments
Windows Management Instrumentation (WMI) is the thing you can use. For instance you can use the following code to get BIOS id's of the system.
ManagementObjectSearcher searcher = new
ManagementObjectSearcher("root\\CIMV2", "SELECT * FROM
Win32_BIOS");
foreach (ManagementObject wmi in searcher.Get())
{
Console.WriteLine("BIOS Serial Number: " +
wmi.GetPropertyValue("SerialNumber").ToString());
}
Similarly you can get other system information and work with it to generate a unique id of a system. Here is a good article on CodeProject from where you can take help. Please have a look.