Also, there are free software programs (via web) that will erase drives and overwrite them to “military spec” so the original info can’t be pulled off the drive. But, in all reality, smashing it does the trick.
Or take the hard drive to Best Buy’s Geek Squad. Tell them you’re having trouble reading some of the material on the drive. They will be sure to erase the whole drives and make it completely unusable or recoverable. :-)