New to Codeigniter Error issue with Login and Register code

It sounds like your database driver is not being loaded  ... $this->load->library('database'); or autoload it.
Further, your class name may work on WIndows, but you will have issues with the non-UCfirst name if you deploy to a Linux server; the class name should be Model_users.

Thanks for your help the problem was in $autoload['libraries'] = array('database', 'email', 'session');
the array was not loaded with information.
Now working fine  thanks

I bet us newbies keep you busy with crazy questions??