@JaneAir - I don't blame you for being worried! Hard disk problems can sometimes mean the end for a computer.
Fortunately though, there are ways to recover data from a corrupted hard drive. Sometimes this results in a fix for the computer, and sometimes it just results in the user being able to recover some of their files to put on their next machine.
Although sometimes the computer can't be fixed and the data is all lost. That is a bitter pill to swallow, let me tell you. Especially when you forgot to back up your data!