string path = System.Environment.SystemDirectory; 
            path = path.Substring(0, path.LastIndexOf('\\')); 
            path = Path.Combine(path, "Microsoft.NET"); 
            // C:\WINDOWS\Microsoft.NET\  
            string[] versions = new string[]{     
                "Framework\\v1.0.3705",     
                "Framework64\\v1.0.3705",     
                "Framework\\v1.1.4322",     
                "Framework64\\v1.1.4322",     
                "Framework\\v2.0.50727",