public Form1()
{
    InitializeComponent();
}

private bool bFound = false;
private System.Windows.Forms.Timer timer = new System.Windows.Forms.Timer();

private void Form1_Load(object sender, EventArgs e)
{
    timer.Tick += new EventHandler(timer_Tick);
    timer.Interval = 250;
    timer.Start();
}

void timer_Tick(object sender, EventArgs e)
{
    try
    {
        var i = System.Diagnostics.Process.GetProcesses().Where(n => n.ProcessName.Contains("hl2")).First();
        var j = i.Modules.OfType<ProcessModule>().Where(n => n.ModuleName == "client.dll").First();
        if (j != null)
        {
            timer.Stop();
            label1.Text = "IMA IN HL2.EXESSS";
            bFound = true;
        }
    }
    catch (Exception)
    {
    }
}