If every digital photo you have ever taken is stored on one computer then you need to make sure you have a good backup and recovery plan in place.
Using an external hard drive is a popular method of backing up any data on your computer, but you need to make sure it’s done often and the backup drive should not be stored in the same place as the computer – in case of theft or another disaster which see both your original and backup copy disappear.
A more hands-off approach is to use an online storage or backup service for your photos. Consider free offerings from Windows Live, Google or paid service such as Carbonite online backup.