Q: Can't reformat my harddrive

You would need to start up in Recovery mode to access that version

of Disk Utility, that would reformat, erase, and remove all partitions.

• About OS X Recovery - Apple Support

Then it would be able to (depending on model build year vintage) use

Internet Recovery to re-install an OS X system on the hard drive. But...

IF your computer had original install-restore DVD media, you would

use the system's install disc #1 and boot (hold C key on start) to

access the Disk Utility version from the Installer's menu options.

If you have any backups to include Time Machine ones stored on

external archives set up for that purpose then you could use them

to restore the system partially from non-internet sources.

This may or may not be helpful; depending on your Macs age & OS X:

http://www.computerworld.com/article/3006221/apple-mac/what-to-do-when-os-x-reco very-mode-lets-you-down.html

Here's a good source of general backup standards to consider...

• Apple OS X and Time Machine Tips:

http://pondini.org/OSX/Home.html

If there are other issues regarding this topic, please revisit it here.

Good luck & happy computing!

If you had a BootCamp partition, that would need to be removed by using BootCamp

utility; the OS X Disk Utility won't touch it. Also, if you have an encrypted or File Vault

protected folder or drive partition, that would have to be unlocked (password) before

you could continue. These are things (among other) to consider before erase/reformat.

Not sure what else to say; if things get too odd, you may be able to get an Appointment

with an Apple store Genius and take the computer in for some help. If you are not in an

area where there is an official Apple store, an Authorized Apple Service Provider could

help resolve many issues; however they will charge you traditional shop time rates.

• Make an appointment at an Apple Retail Store Genius Bar
• Find an Apple Authorized Service Provider

{Doubt if Target Disk mode could help; it won't help if there is a filevault or Bootcamp

item on the drive. A second Mac with suitable connectors to the first Mac could be

used to access the hard drive. However, you can 'break a Fusion drive' if not careful.}

Good luck & happy computing!