Process error

I create this message in program:

Failure in AutoExtract for switch set to Monthly 

Then program returns this error:

System.ComponentModel.Win32Exception (0x80004005): The specified executable is not a valid application for this OS platform.

   at System.Diagnostics.Process.StartWithShellExecuteEx(ProcessStartInfo startInfo)

   at System.Diagnostics.Process.Start()

   at AutoExtract.AutoExtract.ProcessExtract(String msg)

   at AutoExtract.AutoExtract.MonthlyExtract(String path)

   at AutoExtract.AutoExtract.Main(String[] args)

Here is code for that method.

      public static void ProcessExtract(string msg)       
      {
         int retCode = 0;

         //Run program
         Process extProcess = new Process();
         extProcess.StartInfo.FileName = executable;
         Output_Files.PrintLog(extProcess.StartInfo.FileName);
         extProcess.StartInfo.Arguments = runDate;
         extProcess.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
         extProcess.StartInfo.CreateNoWindow = true;
         extProcess.StartInfo.WorkingDirectory = path + "";
         extProcess.Start();
         extProcess.WaitForExit();
         retCode = extProcess.ExitCode;
         extProcess.Close();
         extProcess.Dispose();

         if (retCode != 0)
         {
            string message = "The " + name + " " + msg + " Extract Failed with a return code: " + retCode.ToString();
            Exception ex = new Exception(message);
            throw ex;
         }
      }