Everyone knows how important it is to constantly back up your data. For whatever reasons, people still fail to do so, and when their computers start blowing smoke through their holes, it's already too late.
Working in the design world, file backup is probably the single most important maintenence rule. You ALWAYS want to keep backups of your files, documents, photos, videos, music, and so forth. If you're running a Windows machine, you should be taking note with extra care as Windows machines are more prone to viruses (and other infections).
External Hard Drive are extremely cheap these days! There's no reason why you shouldn't invest in something that can save you hundreds of hours, depression, and tears. Do the right thing and get into the habit of backing up often. There are tons of solutions available out there that will automate this process for you on a daily, weekly, or monthly basis - your choice.
Side note: If you're one of those people that has a million different files and folders scattered on your desktop and around the computer, you need to learn a big lesson. Organizing your files will not only make your backup-process much easier, but you will feel less cluttered when everything is easily accessible.
If these solutions are not suitable for you, a simple Google search (or a Bing.com search) will help you out.