[brcos]

Is there an application for Imac/OS X that will overwrite or wipe unused disk space like Eraser and BCWipe do for PCs?

I am aware of the Secure Empty Trash feature of Safari, but as I understand it not everything goes to Trash (deleted emails, cleared History or, obviously, anything from Firefox). So if I want to give my Imac to a relative or donate it to charity, is there any software that will let me overwrite unused hard drive disk space with complete confidence that all personal information I have deleted is unrecoverable? Or do I have to remove the drive, smash it with a sledge hammer and start all over again?

[Art Vandelay]

Disk Utility does it.

[Cold Warrior]

Yes it does. And you'll have the option to use multiple passes for different levels of secure erasure.

I erased 30-40 GB on an old external drive recently. It took approx 3-4 hours to complete the 7-pass wipe.

[brcos]

Thanks to both of you. I didn't realize it would be that easy.