I agree it can be fun to take a hammer to the drive. It will break into about 10000 pieces, so the chances of someone trying to put that back together to get your credit card number are pretty slim.
If it is a decent sized drive you may want to go get a $10 enclosure and turn it into a USB hard drive. I did that with an old 160 GB and it comes in handy when I need to save data from someone else's computer and I don't want to take my own backup drive along.