If this is happening when you are trying to turn the computer on, it looks like it is trying to boot from the network card.
Right when the computer turns on you should see something that says press F1 (or something similar) to access the bios, press that key and look for the boot order in the bios. Make sure your hard drive is listed here, and likely you could check to see if the drive is being detected anymore on some tab.
Generally this happens when a hard drive is dead, and no longer being detected and you see the message you got because the nic has always been in the boot order, but just listed below your hard drive.
Contact the manufacture if it's under warranty, if not you may just need to replace the hard drive and reinstall.