When I turn on my notebook, it just keeps saying
Operating system not found
What do I need to do to fix it? It's a NP-N130 Samsung notebook
Make sure that there is no DVD, floppy disk, ZIP disk or whatsoever in your drives when you boot your system.
Should you laptop refuse to boot anyway and this seems to have happened out of the sudden, this might indicate your hard disk failure. You'll need to have your HDD exchanged and install the OS anew. There are chances that you can also restore some data from your corrupted drive, but this can be done only be a trained professional.