Question

I purchased Lion through the app store a while back for my Macintosh and there is no disk. Now I need to reinstall the operating system. How can I do this? I would really like to have a clean install of Lion.

Answer

1. Order Lion on an USB thumb drive from Apple ($69.00) or
2. Make your own bootable disk from the copy of Lion you downloaded (free)

Make your own bootable disk of Lion

What you’ll need:

• The “Install Lion App” you downloaded from the app store
• A thumb drive or DVD 4.05GB or more free space on it.

1. Find the “Install Lion App” that you downloaded in your applications folder. If you don’t have it you can download it again from the app store by going to the Purchases area of the App Store. Even a good connection is going to take the better part of an hour as it is over 4GB. You may want to find something to do or take a break. When it is done installing, exit from the installation prompt. If you install it now, it will do an install and delete the image disk.
2. Right click (or control-click) the program icon and select “Show Package Contents.
3. Go to Contents –> Shared Support –> InstallESD.dmg. The “InstallESD.dmg is the file we will use to create our bootable disk of Lion. Copy/Paste this file to your desktop for easy access. NOTE: Do not drag and drop or you’ll get an alias of the file.
4. Open up Disk Utility (Applications –> Utilities –> Disk Utility).
5. Plug in your thumb drive or insert your blank DVD. Continue to the appropriate section below.

If inserting a DVD:

• In Disk Utility, click the “Burn” icon and then select the “installESD.dmg” file that you just copied to your desktop.
• Let it burn.If inserting a thumb drive:

Select the USB thumb drive you want to use:

• Go to the “Restore” tab.
• In the source area, find and select the “installESD.dmg” file you copied to your desktop earlier.
• In the destination area, choose the partition of the drive you want to use. NOTE: Be aware that you will erase everything on the partition/USB you choose and it will be replaced it with OS X Lion, so be sure you don’t have anything important on it.
• Click Restore.

It’s new installation time!

After the image is burned to your USB thumb drive or DVD, restart your computer while holding down the option key. An option to boot from the DVD or USB drive will appear. Now you can go through the installation as normal.