You will need:
- A Mac running OS X 10.7 - Lion
- To have bought OS X 10.7 - Lion in the Mac App Store (unconfirmed)
- I also strongly recommend backing up your hard drive (be it Time Machine, or whatever)
Firstly, and obviously, you'll want to backup and make sure you have another copy of all your vital files.
Step 1: Boot Into Lion Recovery Mode
Restart your Mac, and hold Command + R(â + R) as it powers back on.
This should take you into Lion Recovery Mode (pictured).
Step 2: Erase Macintosh HD
Choose Disk Utility
1. Now, select Macintosh HD from the list on the left.
2. Select the Erase tab.
3. Then press Erase... to erase your hard drive.
These steps are detailed in picture 2
Step 3: Reinstall Mac OS X
Close the disk utility window. This should take you back to the Lion Recovery Mode screen.
Now click Reinstall Mac OS X to begin reinstalling.
It will likely ask you for your Apple account details, enter them, and the rest of the on-screen instructions are dead easy to follow.
Step 4: Finished
DISCLAIMER: If anythings goes wrong for you, it is nothing to do with me. This instructable is a guideline, not a guarantee of it working. I accept no responsibility if it breaks your hard-drive/computer/or anything.
That said, there's no reason it should do any of that, I've done this twice now and everything has gone as-expected.