What to do with old I MAC?

[CloudWatcher]

5. Scrubbing the disk

Unless you've got state secrets on your hard drive, there's no need to physically destroy the disk.

Two reasonably safe options ...

1) Boot to "recovery mode" (cmd-r during boot) and use the "Disk Utility" in recovery mode to securely erase the disk. You can tell it to scribble zeros over the data blocks, not just a quick erase of the filesystem information. This will leave the "recovery partition" intact, but that's ok ... you don't have anything personal stored there.

2) Depending on iMac vintage, boot to "target disk mode" (hold down T during boot). This will turn the Mac into a big disk that you can plug into a second computer (e.g. another Mac) ... with an appropriate cable. Then you run Disk Utility on the 2nd computer to completely erase the disk of the other Mac. This can zero the whole disk, including the recovery partition. Slightly more complex than option 1 since you need the right cable and a second computer.

And it's not *that* hard to take an iMac apart and pull out the hard drive ... but you'll probably need a suction-cup puller to get the front glass off. And if you're going to go to that much work, you might as well put in a bigger disk and keep using it!