This is the single most important thing that you can do with your computer. It is essential that you back up your data in the event that something should happen to it. Whether it is a computer virus, a hardware failure, a real-world catastrophe (like a house fire-worst experience ever...), you MUST have a back up of your data. There are a few ways to do this. Before we explore my recommended way to do this (for free anyways), I will recommend the best possible scenario.
You should develop a backup routine. If you spend a couple hours in front of your computer at the same time each week, run a backup in the background. It is important to back up your documents, photos, videos, and anything of importance to you. Ideally this will be to an external hard drive, but you can use CD's or DVD's if you must. You can never have enough back ups. You are thinking that the Geek has forgotten something aren't you? What about that fire that you mentioned? I was getting to that. I recommend an online backup solution as well. I use Carbonite and love it, but I would go with Mozy if I were you. It is great! If you don't have alot of data, you can use Microsoft's Skydrive. (Tip: You can have as many accounts as you have emails through them).
So lets figure out how to do this so that we can make it a habit shall we? If you want this to be the easiest thing you can possibly do, I suggest that you pick up NTI backup or Acronis True Image. The FREE-Yay- method we are exploring here is easy as well, it just takes a little more set up. Its nothing we can't get through.

Windows XP
Insert your Windows XP CD into the drive and double click it when it pops up on your desktop.
In Windows Explorer, double click the ValueAdd folder, then Msft, and then Ntbackup.
Double click Ntbackup.msi to install the Backup utility.
Click Backup to run Microsoft's Backup program.

How to Run the Backup Utility
Click Start, point to All Programs, point to Accessories, point to System Tools, then click Backup to start the wizard.
Click Next to skip past the opening page, choose Back up files and settings from the second page, and click Next.
Decide whether you want to back up everything or just certain things.
Decide where you want your back ups to be saved.
Set a schedule for regular backups.

Another Method

1. Set up your hardware and software. Download and install the most excellent free software, SyncBack Freeware v3.2.9(Its near the bottom of the page). SyncBackSE version 4.0 is also available to buy at $25. This tutorial will use v.3 for the cheapies and those of you giving SyncBack a try for the first time. Once your external drive is connected to your computer and turned on, name it "Backup" and browse to it in Explorer. (On my computer, it's the F:/ drive.) Create 3 folders named "Nightly," "Weekly" and "Monthly" We're going to store our backups into these folders.
   
2. Create the backup profile. Fire up SyncBack. Create a new profile called "Nightly Local Backup." Set the source folder to your documents folder, and the destination to your backup drive's "Nightly" folder, like this:
   
3. Select the directories to backup. You can backup the entire "My Documents" folder, but I didn't want to do that, because I've got about 75 gigabytes of music, photos and video that don't change too much and aren't world-ending in subdirectories of "My Documents." I don't have the space on my drive to keep copies of multi-gigabyte media in triplicate. So I chose the backup "selected subdirectories" option, which lets me tell SyncBack to ignore "My Music," "My Pictures," and "My Video" each night when it runs. To do so, click on the "Subdirectories" tab. If you've got tons of subdirectories, it'll take SyncBack sometime to traverse the tree and show 'em to you. Go grab a drink of water and come back to check off the directories you want backed up each night.
4. Set up e-mail notification of backup failure. Since we're a bunch of smart cookies, enable the advanced options in SyncBack by hitting the "Expert" button at the bottom. To keep tabs on whether or not your nightly backup is completing successfully, in the E-mail tab, check off "E-mail the log file when the profile is done." I don't want an e-mail every day; I just want one if things go awry. So also check off "Only e-mail the log if an error occurs." Set your SMTP server options as well and hit the "Test E-mail Settings" button to make sure you can receive messages. Click to enlarge image.
   
5. Schedule the job. Now hit up the "Misc" tab, and hit the Schedule button. Here you'll tell Windows to run this Nightly backup profile, well, nightly. I set mine to run at 2:00AM every night. Be sure to set your Windows password for this scheduled task by hitting the "Set Password" button.
   
   

 

Wash, rinse and repeat twice for Weekly Local Backup and Monthly Local Backup profiles, but point them at the appropriate directories and also set the schedule to, um, weekly and monthly, respectively. Once you're all set up, you can run each job as a test (it'll take a long time, depending on how much data you've got), or just leave things to run on their own. Once all 3 profiles have run, you'll have 3 copies of your most important data on your external drive getting updated every night, week and month. If something goes wrong and the backups fail, you get an email notification letting you know.

There you have it. That is all that you have to do. Rest easy ladies and gentlemen! You don't have to worry about your data. All you have to worry about is hugging your favorite Geek!