Like the leaves of Autumn, your hard drive will die. Your hard drive is where all you stuff is stored.
Please make sure that the things that are important to you, like your photos, email, documents, addressbook, and financial/tax data are stored in at least two places. If you have a copy on a USB stick, another computer, or an external drive, computer problems are much less stressful, because your data is safe.
Please note that moving your data to an external drive is not a backup. Until your data is in two places, I do not consider it safe.
