For under 100.00 you can get a terabyte or 2 terabyte external hard drive at either Tiger Direct or Buy.com.
I back up everything on my hard drive that I don't want to lose onto an external drive (or two), that way if I have to change computers I can just plug my external into a laptop or a different PC.
When my computer died the last time, I was using an old 15 gig laptop with a 500gig external plugged into it and everything worked just fine til I could afford to replace my computer.