Your notebook can't find your hard disk. Enter the BIOS to see if it's detected. Try reseating it, too. If you've another computer/external hard disk enclosure, plug the disk into that and see if it detects it. Otherwise, your disk may be dead or damaged. That's when you run a diagnostic on it - I'd suggest one from the Ultimate Boot CD.
Can you get into your BIOS? If so, go and remove LAN as a boot option or make it the last option. Priority should be CDrom - HDD - Floppy - and so on. This should end your problem. If you are technically inclined you can set your priority as HDD-CD/DVD-Floppy-etc. If not you may be suffering a hardware problem such as a failing hard drive.