Backup your data, now.
I'm not kidding, right this minute.
Stop reading this and go backup any important digital data you have. Hard drives can fail. It happens everyday. People lose important documents, pics, videos, music, etc. all because they trusted their one storage solution.
I give you this advice, because I was reminded of this lesson this week.
I was fortunate though. Almost everything I had on that drive was either backed up elsewhere, or I still have the original CD's that I can reload. So far, I only know of 1 important thing that was lost. My tax files. I'd done our taxes on turbo tax for the past 5 years. Sadly, I think somehow that was the only place I had those files stored. I'm hoping I made a hardcopy last year of the actual returns, but I don't have a good feeling about it.
Today I will be purchasing a new external drive (maybe 2 =), and making sure I have multiple copies of everything. You should do the same.