It is my wild assumption that those without computers are not reading this site. Perhaps that's a trifle bold of me, but I feel strangely confident in proceeding with a whole week devoted to getting your digital ducks in a row.
First, always first: make backups!
Here's a helpful page to remind you of the kind of files you should back up.
Remember that in addition to physical media under your control – external drives, CDs, DVDs, second computers – you may also have some space for things on a hosted service. For example, if you own your own domain and have hard drive space on a server you could put some backup information. Just remember that if that service goes out of business the backup could be lost to you and that if it gets hacked, personal data could be stolen. Be selective about how you use these resources.
It's advisable to make a couple big backups periodically on separate media (e.g. onto CD or DVD and onto an external harddrive) and store them in separate locations.
Regularly – every week or at least every month is advisable – make a backup of those things which have changed since the last backup. When you do this backup, I recommend keeping the previous one or two backups. That way, should you lose your current information and turn out to have a corrupted backup, you still have the prior one.
Doing backups can be tedious and is easy to put off, so figure out a good system that works for you and make sure you have the supplies you need. Get help from a geek friend if you're not sure of the process or the best approach for you.
Build time into your schedule to do backups regularly. It may seem like a hassle, but compared to the loss of all your personal files, it's not a big deal at all.
Discardia 