Remove the harddrive from the machine. Get a good, hefty hammer. Preferably a claw hammer as it may come in handy in step 4. Bash the fuck out of the harddrive casing until it pops open. Yank out the disc itself. Bash the fuck out of the disc with the hammer. Bend the disc, if possible. Better yet, break it. Throw the disc away. Put the hammer back where you got it. Have a cookie, non-digital variety.
Oh, how I miss the early 2000’s (2000 - 2004, to be exact). Ha.