Your hard disk will crash. Count on it. It happens to everyone sooner or later. And when it does you will be happy you have a backup copy of all your data and important files. You have an up-to-date backup, don’t you? You don’t? No worries. Here are the simple rules of data recovery for people who hate to back up.
I recommend using removable media or a cloud service for your backup. If you can’t take it with you, it’s not a backup. I know a famous author who lost an entire novel because her backups were stored next to the computer when her house burned to the ground. You can back up to DVD or memory stick if you have no other choice, but a cloud backup is the best option because most people will put off backing up until it’s too late.