Error trying to access a file in XP

    private string obtenerMD5(string sArchivo)
    {

        string sMd5 = "";
        Process compiler = new Process();

        compiler.StartInfo.FileName = "c:\sys\progs\md5 ";
        compiler.StartInfo.Arguments = sArchivo;
        compiler.StartInfo.UseShellExecute = false;
        compiler.StartInfo.RedirectStandardOutput = true;

        compiler.Start();

        try
        {
            sMd5 = compiler.StandardOutput.ReadToEnd().Substring(0, 32);
        }
        catch (ArgumentOutOfRangeException e)
        {
            MessageBox.Show("No se encontró archivo en ésta ruta: " + sArchivo, this.Text, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
            bHayError = true;
        }
        return sMd5;
    }'

This method receives the address of a file with a .DLL extension which is selected from an OpenDialog. Executing the code from the windows 7 operating system there is no problem, but when you want to try it in XP the error jumps.

I do not know if it could be a permit problem or something else.