using System.Diagnostics;

This namespace provides access to local and remote processes and enables you to start and stop local system processes.

protected void Button1_Click(object sender, EventArgs e)
{
// string str = @"C:\windows\system32\notepad.exe";

// string str = @"C:\windows\system32\winamp.exe";


string str = @"C:\Documents and Settings\RAJ\Desktop\MCNewsLetter\SendNewsletter.exe";
Process process = new Process();
process.StartInfo.FileName = str;
process.Start();
}