The two possible solutions: a new hard disk or a new motherboard. Or maybe just reseat the cable between motherboard and hard disk.
Since you're inside the normal year warranty (maybe you have even 2 years) it's clear what to do: back to the shop or to Acer Customer Service and have it repaired.

There's a good chance you'll lose all data on the hard disk. But you made backups, didn't you?

Kees