In criminal cases I've read of defendants purchasing several commercial data scrubbers and still the cops were able to retrieve everything. I wonder if the products mentioned really work.
A thorough dunking in the river or lake should work well, providing you don't remove it after the dunking.
Yes and no. It depends on how the program "destroys" the data. Where I work we have to clean certain hard drives so as to prevent Social Security Numbers from being retrieved. Just formating, even 10-20 times does not prevent recovery. We use a program that writes, overwrites, and overwrites again a total of 35 times as well as scrambling the 1's and 0's dozens of times. We run the program twice to be sure the hard drive is clean.
Lately though we've decided it was easier to have the hard drives removed and placed into an industrial shredder and ground into nearly a fine power. A lot quicker and easier.