I assume you have a PC and not a Mac. I also assume you have your Windows installation discs and your other discs in case your hard drive dies. You therefore want to back up your data files. If they're in a "My Documents" folder, look at the size of that folder. If it's small enough, you could back it up to a USB drive. Otherwise, get an EHD (external hard drive) that comes with backup software. Then it's super easy: once you do the initial backup, you can then schedule incremental backups, which take far less time.
An alternative is to create an exact mirror of your hard drive. You'd need an EHD that's the same size, and mirroring software such as Norton Ghost. None of this is difficult.
On my Mac, I have a program named Super Duper, which performs nightly incremental backups to an EHD. Because I have a sizeable investment in digital music, I separately perform a monthly incremental backup to a portable EHD, which I then unplug and keep in a closet. This is to protect in the event of a power surge.