Backup would mean more than one device/media/medium. What you have would be a fine first copy but fails accepted definitions of backup.
Not only that but read our forums where people used external hard disks as storage and lose everything.
But to answer your question. Read the next 2 links:
That should get you started and let's hope you create a backup set you can trust.
I recently bought a EHD for my computer, and was going to do some backing up. I did a search that says that the Home edition of XP has a backup feature, so I looked up on my PRO and found one under system tools. It was ok, but is there any better backup programs I can get my hands on?
I have norton 360, but that only backs up on nortons website, I am trying to use my external HD.