After taking advice from people on JKLatics, I have decided to remove my hard drive from my old pc and smash it to bits with a hammer before taking it to the tip.
I was very proud of myself for getting the cover off and being able to see inside, but I'm not 100% sure what my hard drive looks like. There are a couple of flat green bits (motherboard??), and I have unscrewed and removed one block thing, which I have just noticed is my Floppy drive . The other block thing just below it looks like it might be hard driveish - is this likely? it's sort of green underneath, with a load of black squares surrounded by silver metal. On the top, it sort of has a silver circle thing.
Can anyone confirm this is the bit I need to smash up? (Also, is this the only bit I need to smash up in terms of security, etc, before dumping it?)
Cheers!
(sorry this is a bit rambly, I'm clueless when I start taking things apart)