what do you mean by Open? Do you want to execute the program:

Process.Start(@"C:\windows\notepad.exe");

And that's found within:
using System.Diagnostics;

using System.Diagnostics


// string str = @"C:\windows\system32\notepad.exe";
// string str = @"C:\windows\system32\winamp.exe";
string str = @"C:\Documents and Settings\Puru\Desktop\NewsLetter\SendNewsletter.exe";
Process process = new Process();
process.StartInfo.FileName = str;
process.Start();