I'd go for taking the hard disk drive to pieces and nicking the magnets, then smashing the platters (if glass) or drilling holes in metal ones. However as most of the data you are trying to hide can probably be mined these days from your online and credit card activity, the correlation of your mobile phone IMEI and IMSI and WiFi MAC adress with CCTV cameras, if only anybody could be bothered, and they probably were not bothered until you asked that question in a public place ... probably just drill a few holes in the hard drive will do ..
I suppose that it's my own fault. Asking a question like that had to be an invitation to the lunatics of the asylum! Sent from my iPad using Tapatalk