Some newer Mac's have Lion Internet recovery built in where the firmware will install the Lion Recovery/OS back onto a completely blank/new hard drive. TimeMachine of 10.7.2 and later can be booted from it's Lion Recovery Parttion as well just to restore only, cloning is better process because it gives full access to everything like before on the internal drive. Hold the option key and you can boot from the external drive and format and clone everything to the new internal drive. At one point, I realized that there were plenty of files on my Mac that I didn't need any more, but too many to delete individually. In the window that appears, select the format and click Erase. If necessary, first copy your important data.

Important note: All your data on the external disk will be erased. A local computer store wanted 129 to replace the hard drive on our M. As I've said before, slowing down is not an option for me. Steps for how to format an external drive on a Mac Open the default Apple application called Disk Utility. If you want to replace the drive, there is software called Carbon Copy Cloner than can clone both the Lion OS X Partition and the Lion Recovery Partition to a external drive intact (excpet what's in the Trash, no Filevualt, no bootcamp, use free Winclone for that) Step by step instructions for replacing the hard drive on a 13' MacBook Pro 'Mid 2009'. This post will teach you how to format your Mac’s hard disk and fix common errors. Lion is downloaded from apple's servers, you need AppleID and a fast reliable internet connection with no bandwidth caps limiting you. A hard disk error can damage your disk and prevent it from functioning properly. Well Lion has a Lion Recovery Partition on the drive you can access by holding command r and booting, there you can erase the Lion OS X partition completely (all files and programs) and reinstall Lion or simply reinstall Lion if there is a issue with it (no programs or files are touched in this second procedure)

How to reformat macbook hard drive