Thanks for your quick reply. I'm a real novice and cant "translate" your instructions. I dont have a cable to connect it to my new imac. Dont know what you mean by formatting a disc or what disc utility is. By opening it, do you mean taking it apart? I'm not sure I have the tools to do this. When people recycle or throw out computers, do they usually erase the hard drive? What would happen if I just took the hard drive icon on my desktop and dragged it to the trash and then emptied the trash. As I said, there really isnt anything important on this drive. Its such an old computer, i think they will just use it for scrap metal.
As WALTER-MILANO-ITALY indicated above, it is possible to gain access to the hard disk on another computer using FireWire target disk mode (if both machines have FireWire ports). A FireWire cable would be needed for this. See the manual for your computer(s) and the article below for details.
In order to remove a hard drive, you would have to disassemble the computer. This can be more or less difficult (a quick look at ifixit.com should give you an idea about this) depending upon which model it is.
Once the hard drive has been removed, you can either keep it, erase/use it with another computer, or mechanically destroy it. If you wish to connect it to another computer, something like this example could be useful:
You are not supposed to drag a hard disk with an active system to the Trash. Dragging individual files to the Trash (and emptying the Trash) is not going to be sufficient, unless the space is overwritten. It is not wise to recycle a computer without having properly erased or removed the hard disk drive.