recovery fail

long story short, I recently had a problem with my laptop and had to erase/wipe it out, even tho I had to back up ! but I need my laptop for my up coming exams and can't wait for an Apple genuise bar apointment. It all went fine and I started downloading my itunes and stuff, but the next day I woke up to find out that my laptop was wipedout again and displaying a grey screen with a questoin mark inside a file shape, when tying to boot into recovery mode and after clicking on reinstalle and going through the prosses, it just doesnt give me any HD as an option to download/installe OX S and I'm unable to find a HD disk on the Disk Utility. please help !!