My Mac is broken

I had a nine o'clock lecture this morning so I was out of the house by 7.30.daughter #1 came home from school really excited having coming third in the science ' design a roller coaster' project.
The girls had kayaking after school and they had supper there. When I went to the sitting room to ask my son what he wanted for dinner, I found him fast asleep on the sofa. Later on, he told me that he was feeling unwell.
My iMac started to play up last night and wouldn't boot up. Before leaving for work this morning I switched it on but when I came home from work, it still hadn't booted. I spent an hour on the phone with apple support trying to identify the problem. It seems that my hard disk is knackered. I am not a happy bunny.