Well get an external HD big enough for your hard drives in use to be copied to, or if you have a CD-RW drive or DVD-R drive back it up to those. If you're using optical media it's usually best to use RW formats so you're not stuck with different versions of your hard drive and having to buy new discs constantly. If you go the external HD route or DVD-RW route, you can also use a backup script or program to back your hard drive up every night/week whatever. Otherwise you'll have to do it manually whenever you want to back up.
I have both an internal (13 gig) and an external (60 gig, 4 partitions), so i back my most important files up back and forth. That way if one fails, i'll have the most important stuff on the other one, too. i don't do full backup of both drives because it would just be wasteful, if i had a HD big enough to back both drives up to, i'd rather just use it for everyday stuff. There's not a lot of point to backing up programs that you have discs for, it's your files you should worry about.
🙂
pnw