Код вывода большого количества разной информации о операционной системе, в том числе ее версию, номер сервиспака, количества свободной памяти и многое другое:
using System;
using System.Management;

namespace test
{
class Program
{
public static void Main(string[] args)
{
        ManagementObjectSearcher searcher5 =
        new ManagementObjectSearcher("root\\CIMV2",
            "SELECT * FROM Win32_OperatingSystem");

        foreach (ManagementObject queryObj in searcher5.Get())
        {
            Console.WriteLine("-----------------------------------");
            Console.WriteLine("Win32_OperatingSystem instance");
            Console.WriteLine("-----------------------------------");
            Console.WriteLine("BuildNumber: {0}", queryObj["BuildNumber"]);
            Console.WriteLine("Caption: {0}", queryObj["Caption"]);
            Console.WriteLine("FreePhysicalMemory: {0}", queryObj["FreePhysicalMemory"]);
            Console.WriteLine("FreeVirtualMemory: {0}", queryObj["FreeVirtualMemory"]);
            Console.WriteLine("Name: {0}", queryObj["Name"]);
            Console.WriteLine("OSType: {0}", queryObj["OSType"]);
            Console.WriteLine("RegisteredUser: {0}", queryObj["RegisteredUser"]);
            Console.WriteLine("SerialNumber: {0}", queryObj["SerialNumber"]);
            Console.WriteLine("ServicePackMajorVersion: {0}", queryObj["ServicePackMajorVersion"]);
            Console.WriteLine("ServicePackMinorVersion: {0}", queryObj["ServicePackMinorVersion"]);
            Console.WriteLine("Status: {0}", queryObj["Status"]);
            Console.WriteLine("SystemDevice: {0}", queryObj["SystemDevice"]);
            Console.WriteLine("SystemDirectory: {0}", queryObj["SystemDirectory"]);
            Console.WriteLine("SystemDrive: {0}", queryObj["SystemDrive"]);
            Console.WriteLine("Version: {0}", queryObj["Version"]);
            Console.WriteLine("WindowsDirectory: {0}", queryObj["WindowsDirectory"]);
        }

        Console.Write("Press any key to continue . . . ");
        Console.ReadKey(true);
}
}
}