Big ladle of molten steel
If any part of the drive remains, it could lead to the building of Skynet and bring about Judgment Day.
Look at
Protecting your computer from the NSA, but in the mean time if you want to destroy the data and the drive, open it and remove the disk platters. Take the platters and burn them with a propane torch. Another method is to use a bench or hand grinder and remove the coating on the disk platters. The 3rd method is to punch a hole in the drive and fill it Drano (wear gloves) and let it sit outside for a week. Disk cleaning software DOES NOT WORK, don't trust it. Smashing the drive does not work either, fragments of a disk drive can contain years of data. I would also worry more about what data you have already disclosed to big brother via Windows OS...