When an old system needs to retire, it's important to make sure that data doesn't just walk away and land in the wrong hands.
I would recommend that you pay for a service or program that wipes your data and makes absolutely sure that it's gone forever.
In my case, I had an old laptop that had been sitting around forever. It was used at home, and it died a horrible death a while back - keyboard destruction by small child comes to mind. It never booted since whatever he did...
Anyway, house cleaning is a wonderful thing. I recycled the laptop, but yanked the hard drive.
Here's what my son and I decided to do. If you decide to do something similar, wear protective eye wear, and don't blame it on me. ;)
Perfectly good, and defenseless hard drive. Its only crime - hosting personal data:
Small bits of data, or shards of had drive:
Data destruction accomplished in 70 micro seconds - that's the time it took the arrow to travel 1/4 inch through the hard drive.
Video of the destruction: