Thanks so much everyone. It is certainly still under warranty - only got it from PC World (big mistake - I know now) on 11th Nov. Have had nothing but aggro from them, after trying for ages to get though to anyone helpful. They were supposed to order a new drive, but when I rang back a week later, no drive had appeared. Bet they didn't bother to order it.
Upshot is that an engineer is coming on SUNDAY and if he can't fix it, they need to take the computer away. I have refused this as I need it to live - my disability means I need it for everything from shopping to prescription ordering to keeping in touch with friends and my 89 year old mother in Australia. I just can't be without it, so if they can't fix it, I will demand a new computer (can they change the hard drive over?)
Is there anything I can do myself to check if the cable is loose or will the engineer need to do that? I have ordered, from Amazon, an external drive in case they can't fix it and will also try the software recommended. I would like 2 drives anyway as that is what I've always had.
Many thanks again - this is a brilliant forum! Pollyanna