How long will it take to wipe it based on most secure settings?

When you do a secure erase, you can select 1x, 7x or 35x overwriting.

Writing over the data 7 times meets the U.S. Department of Defense (DoD) 5220-22-M standard for securely erasing magnetic media.

Disk Utility will show you an estimate when you kick off the erase process, so you can estimate the time yourself, and cancel out of the erasing process if necessary. Try the 1x ("zero out") option first, and look at the estimate. The 7x overwrite will take 7-8x as long.

A little more info is here -> About Disk Utility secure erase operations

Are you saying you want to use the 35-pass option? I just wiped a 250 GB hard drive with the regular option and that took about 2.5 hours. Using that as an example, yours (at the regular option) should, presumably, take about half that time or 1.5 hrs at most - multiply that by 35 since it will write zeroes 35 times for the most secure option: a guess would be about +/- 50 hours?

It's for the terminally paranoid ...

Yes. But make sure when you erase, that you reformat it as Mac OS Extended Journaled.

Are you selling/donating this Mac to someone else? Is that why you want to wipe the drive?

If you are keeping the Mac and just want to erase the disk before reinstalling Snow Leopard, you don't need to bother with zeroing out the drive. Just do a simple erase and reformat it as Mac OS Extended Journaled. It will only take a few seconds.

stanwelks wrote:
I want to wipe my Snow Leopard with the strongest level of secure wipe on the Snow Leopard install disk.

I will do this on my one year old Macbook Pro that has a roughly 120 GB hard drive.

Any idea how long that would take?

Forever + one day

After it is done wiping, the hard drive has nothing on it, so will the Snow Leopard disk enable it to reload the OS at that point?

If all you want to do is reload the OS, you don't need to do any of that. Just repartition the drive - takes 10 seconds.

Create a new admin account, if possible, and delete your old account. If you can't create/delete accounts, you'll have to delete your address book files and mail manually. Then, use Disk Utility to wipe free space. Use the lowest security setting.

When you are done erasing the hard drive, your install CD will be in the drive anyway; simply quit Disk Utility and it'll return you to the OS Installer. At that point, just go ahead and reinstall. I would not just erase free space; depending on the info you had on it, either a 1x or 7x pass is fine and it should take from about 1.5 hrs (for a 1x) or 10 (?) hrs for a 7x. Plus add another hour or so for a complete reinstall.

Unless you're worried that the person who will inherit your computer is a CIA spy who will immediately cart the machine off to a clean room, disassemble it and recover your deleted data, there's really no need to go higher than 1x. That should be all it takes to prevent the new owner from recovering files using file recovery software.

I agree with Thomas A Reed, & more importantly so does NIST (the National Institute of Standards and Technology). From page 6 of http://csrc.nist.gov/publications/nistpubs/800-88/NISTSP800-88_rev1.pdf (emphasis added):

"Advancing technology has created a situation that has altered previously held best practices regarding magnetic disk type storage media. Basically the change in track density and the related changes in the storage medium have created a situation where the acts of clearing and purging the media have converged. _That is, for ATA disk drives manufactured after 2001 (over 15 GB) clearing by overwriting the media once is adequate to protect the media from both keyboard and laboratory attack_."

More info: The DoD 5220-22-M standard is often misunderstood & regardless, it is obsolete. It actually specified a range of secure data erasing methods for various media types, depending on the sensitivity of the data. For HD's, a single pass overwrite was acceptable for clearing data, the lowest level of secure delete. For sanitation of up to "Confidential" level data, 3 passes (first with any character, then with its complement, then with a random character) followed by a verify was the recommended procedure. For "Top Secret" data only degaussing (demagnetizing) the drive or physically destroying it was acceptable.

The 35 pass erase, also known as the Gutmann method, is *totally unnecessary* for all modern drives. From the epilog of Gutmann's Secure Deletion of Data from Magnetic and Solid-State Memory own paper:

"For any modern PRML/EPRML drive, a few passes of random scrubbing is the best you can do. As the paper says, "A good scrubbing with random data will do about as well as can be expected". This was true in 1996, and is still true now."

_The bottom line_: the single pass erase is adequate for almost anybody's security needs. For those that it isn't, physical destruction of the drive's platter by incineration or grinding it into pieces no larger than about 1/8 sq. in. is the only 100% reliable alternative.

stanwelks wrote:
Thanks everyone for the responses. What if I just make a new account on the computer, and delete my existing one. Would that take care of making the data not easily recoverable?

Not necessarily. You would only wipe out the contents inside your Home folder, but not one level up in the computer's core system settings, which can contain additional information that is specific to your home/office (network configuration, passwords, caches, application settings, etc).

You really should reformat and reinstall so that it's in fresh-from-factory state and the new owner must enter all information from scratch and to guarantee that none of your previous system info is carried over.

Network 23 wrote:
You really should reformat and reinstall so that it's in fresh-from-factory state and the new owner must enter all information from scratch and to guarantee that none of your previous system info is carried over.

This is the best advice. Your original information would be virtually irretrievable. Plus, the new user would get a fresh install with no baggage from a previous install.