Вот один быстрый и грязный метод, использующий классы System.Management.
using System;
using System.Collections.Generic;
using System.Text;
using System.Management;
namespace ServiceTest
{
class Program
{
static void Main(string[] args)
{
string theServiceName = "My Windows Service";
string objectPath = string.Format("Win32_Service.Name='{0}'", theServiceName);
using (ManagementObject mngService = new ManagementObject(new ManagementPath(objectPath)))
{
object[] wmiParameters = new object[11];
wmiParameters[6] = @"domain\username";
wmiParameters[7] = "password";
mngService.InvokeMethod("Change", wmiParameters);
}
}
}
}