Because installation takes place entirely from within the Mac App Store, the usual ‘clean install’ option isn’t present. If you’ve followed our guide for preparing your Mac for Lion, you’re probably in good shape to proceed with an upgrade. If, however, you long for the ability to do a clean install without having to first install Snow Leopard and THEN install Lion, Mashable has you covered.
If you want to create a bootable USB stick or burn a DVD of OS X Lion, read along.
Step 1: Download Lion From the Mac App Store
Go ahead and download OS X Lion from the Mac App store. This is a nearly 4GB download, so if your Internet connection isn’t super fast, you may want to plan to get some other stuff done while you wait.
As soon as the download is complete, exit out of the installation prompt. We don’t want to do an install right now.
Step 2: Find The Install Lion App in Finder (in Your Applications Folder)
Locate the Lion installation program.
Step 3: Right-Click on the Installer, Select ‘Show Package Contents’
Right click or control-click on the program icon and select ‘Show Package Contents.’ Now, you want to browse to the ‘Shared Support’ folder inside of ‘Contents’ and locate a file called ‘InstallESD.dmg.’ This is the file we will use to create our bootable Lion image.
Copy this file to your desktop or another folder you have easy access to.
Step 4: Start Disk Utility
Open up Disk Utility (it’s in the Utilities folder in Applications). At this point, you should see the various hard drives connected to your Mac. If you haven’t already plugged in an empty USB thumb drive or a hard drive with an empty partition, do that now.
Step 5a: Insert a Blank DVD
For users that want to create a DVD for installation purposes, go ahead and put it in your Mac.
In Disk Utility, click the ‘Burn’ icon and then select the ‘installESD.dmg’ file that we just copied to our desktop.
Let it burn.
Step 5b: Select the USB Drive You Want to Use
Click on the tab that says ‘Erase.’
If, however, you’d prefer to create a bootable USB drive. Select it now.
In the source menu, select the ‘installESD.dmg’ file we already copied to our desktop.
For destination, choose the partition of the drive you want to use. Be aware that you will erase everything on this partition and replace it with OS X Lion, so be sure you don’t have anything important on that drive or partition.
After the image is burned to USB or DVD, restart your computer by holding down the option key. You will now be given an option to boot from the DVD or USB drive. Go through the installation, ready to enjoy a new, clean install of Lion.