While "smashing" the hard drive will keep anyone from getting your data, the memory does not retain anything. Once the power is turned off the memory is wiped out, nothing there.
Having said that I have been converting old PCs to LINUX. It is a free operating system that just works. It gives old PCs new life. If you do not use any "special" Windows programs (I.E. Quicken, TurboTax, Autocad or thing like that) then it will work for you.
I replace your hard drive with one that has LINUX on it, I copy your file, music, pictures, etc. to the LINUX drive. Since I use old drives for the next person, I can erase your old drive while there or you can give me $50, which I will give back to you once I get your old drive (which I will erase in front of you).
JoelJohnson530@gmail.com