That is unfortuante news and hopefully your hard drive can be retrievable somehow.
Back-ups of your original files should be made as soon as possible and an external hard drive is one option but should not be the only source.
Copies should be burned onto DVD's or CD's and stored in at least two places. One place should be with family or friends who do not live in the same area as you do. It would do no good to have back-ups made in the same dwelling or town albeit that a natural disaster comes about.
Overkill some would say but one never knows and it all really depends on how important your files are to you.