If you're not backing up your data on a regular basis... you need to be. Whether it is burning to CD or DVD or paying for some online backup service, you need to store your stuff somewhere else. Best option for most people? Just buy an external hard drive... you can even get one of those "one touch" backup ones.
Trust me though, if you do not back up your stuff, you will lose it.
I learned it once the hard way. Back in college, I was slowly learning a bit more about computers and decided to buy a second hard drive for my computer to store my data on in the off chance that Windows shit the bed or some other problem happened upon me. Little did I know, that data drive would fail. It did. I lost all of my crap. ALL of it.
I may have moved my data off of my Windows drive, but I wasn't really backing it up. You can bet your ass I was after that happened. Do I need to mention that I see hard drives fail at work all of the time? Sick thing is that every user at work gets there own network share to store data that is backed up EVERY night. They don't use it.
Need more proof? My main hard drive died Friday night. I noticed a warning on my laptop about my data share being disconnected. Ignored it. Later noticed the famed "blue screen of death" or BSOD on my desktop. "Unknown hard error" was the message. I rebooted - nothing. NTLDR error. Fuck.
Still detected in the BIOS OK. Just wouldn't boot. I feel like my computer was rebelling though - I just ordered a legit copy of Windows 7 Professional. It somehow knew... and more or less told me to fuck off.
Took my drive out and put it into a USB SATA dock and connected to Jen's laptop (booted to Windows). Ran the Western Digital Data Lifeguard tools and it failed. Miserably. Thankfully it's still under warranty and I've already submitted for an RMA. Drive should be here this week (along with my copy of Windows).
So ya, backups. I keep my data on a second hard drive and have a third hard drive to function as a backup. It works. My data still exists... Windows is fucked, but my data is good.