I can't stress this enough: back up your work.
When is the last time you backed up your mission critical files? If your computer's hard drive died today, what would you lose?
There are many ways to back up data.
--Burn a CD or DVD
--Use a flash drive
--Backup to an external hard drive or a networked drive
--email an attached file or files to your email address (gmail is good for this given all the storage space it provides)
--use an online file storage service (There are several free versions--I use www.box.net)
The only option that is not viable is to hope you'll never have computer problems. I'm paranoid about file storage and make sure I have multiple redundancies built in. (Can you say belt and suspenders???) We use all of the above. Really. In combination. The only thing we don't have yet (*yet*) is a regularly scheduled whole machine automatic backup to our 'server' computer. That's next on my list-of-things-for-hubby-to-do.
Make sure you have anti-virus protection that you update regularly and use on a routine basis.
Use spyware programs as well.
Recently, my friend's computer ground to a complete halt because its hard drive needed a thorough defragmentation. Call it spring cleaning.
If you use a PDA, don't forget to back that up regularly. A few months ago, my palm died--out of the blue. I was on vacation in Oregon. (I live in Boston.) I had a panic attack until I realized I had all but the past day's data on an SD card I use exclusively for the PDA's backup. A few minutes later, and my data was back and the PDA has worked flawlessly since. Cosmic ray? Bad luck? Cursed pirate gold? Who knows.
So repeat it all after me:
Do it tonight.
Don't make me come over there.