What prevents you from selling it?

I know of no laws here in the states that prevent a citizen from selling any hardware that they own. Not yet, anyway.

A good thing that we can do with old hardware is to donate to thrift stores, Salvation Army, Goodwill, etc. and you can also ask for a receipt to be used for income tax deduction purposes as well. There may be someone in need of that stuff that is older, never know.

With hard drives, though, I won't let one get out of my hands that hasn't been erased in full and run a program that rewrites all to zeros. Otherwise, I just drill a couple of 1/4" holes through the entire drive and through the platters, and dispose of it. This is to protect things like passwords, credit card numbers, personal info, etc. Don't let that get away from you, the baddies that will take advantage of such are everywhere, unfortunately.

--Mac