Erase MacBook’s hard disk drive, and reinstall OS X as we explained. Once installed, you can connect it to your MacBook, and boot it using external hard drive. Follow the same process what we discussed earlier to install OS X on an external hard drive. If your MacBook is Password Protected OR you don’t remember and unable to reset, you need to use any other MacBook. Now go the partition of the external hard drive where you put OS X setup file, click on it to install and select MacBook’s internal Hard Disk Drive.Make sure Mac OS X Extended (Journaled) is selected while erasing. Once you are inside, launch Disk Utility, select Hard Disk Drive (Mac’s internal hard drive), and erase it.Now select the external hard drive, and boot it clicking on the arrow sign.Your external drive should appear, if it doesn’t, remove USB, and connect it again.Hold the Option Key (alt), and press the power button, hang on until you see some drive on the screen.Once the installation is complete, shut down the system.Now go to the folder where you put OS X file, click on it, and you will be asked to select the drive where you want to install it, click on show all, and select the external hard drive , and proceed to install.Copy and paste the OS X file, onto other partition. One Partition should be erased selecting Mac OS X Extended (Journaled). Connect an external hard drive and go to Open Disk Utility, make at least 2 partitions.Once downloaded, go to Application Folder in Finder, copy it and paste in another folder If you do, the setup file will be removed. Download OS X from Apple App store, but don’t install it.If you know the MacBook login password, but the same password is not unlocking the hard drive to make fresh installation Note : This Process will wipe the hard disk. You may also like to read Microsoft’s misleading statement about MacBook Pro Install OS X on external Hard Disk Drive.Format a Password protected/locked Hard Disk Drive / SSD (Except EFI).Unlock a password protected Hard Drive (Except EFI).Here are the issues that you can fix, and learn This situation may also occur if you forget the password, and unable to reset. Sometimes you buy a used MacBook and realize you can’t reinstall OS X or format it because the hard disk drive asks for the password when you try to boot in recovery mode.

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