Brand new lion and mac air, corrupted!

No, you shouldn't get that message. Something sounds very wrong there. You're only downloading the installer, not the app.

You could try searching to see if the installer still exists in your Applications folder (Look in Applications > LionInstaller.app) in which case you don't need to do any of this. Just click on it and follow the directions.

Failing that, go with your brother's download, though I'm not sure how you're going to get a 4GB file sent to you...

To install on a USB follow the advice from the link Thomas posted above:

Installing Lion on an external storage device

Use these steps to install Lion from your Mac to a different internal hard drive or to an external USB, Firewire, SDHC or SDXC card, or a Thunderbolt storage device.

Important: This will erase the storage device. A storage device that is already formatted to support Windows (formatted for FAT or NTFS file systems) will be reformatted. You should back up any important files that are on the device to a different drive.

1. Attach a USB, FireWire, or Thunderbolt storage device to your computer, or insert an SDHC or SDXC card into the SD card slot if your Mac has one.
2. Launch Disk Utility, from the /Applications/Utilities folder, then click Continue.

Erase and reformat the storage device

1. Click the attached storage device where it indicates it's size in GB.
2. Click the Partition tab.
3. Select "1 Partition" from the Partition Layout pop-up menu.
4. Click Options. Note: Do not select more than one partition.

Click the GUID Partition Table radio button, then click OK.

1. In the format field, select Mac OS Extended (Journaled).
   
2. Click Apply.
3. Enter a name for the drive in the Name field.
4. Verify that you wish to erase and reformat the selected drive by clicking Partiton.
5. After the reformatting process is finished, choose Quit Disk Utility from the Disk Utility menu.

Install OS X LionIf you completed your installation of OS X Lion, your installer may have been removed after your successful first login to OS X Lion. Mac App Store's Purchases page should show Install Mac OS X Lion as being "Installed", and disallow its download, when viewed from a computer running OS X Lion.To redownload the installer on a computer running OS X Lion, press and hold the Option key while you click the Purchases tab. If the button to the right of the Install Mac OS X Lion item doesn't change to "Install" and allow you to download Lion, use Spotlight to search for "Install Mac OS X Lion" on your computer.

1. Launch the Install Mac OS X Lion installer you downloaded from Mac App Store. The installer should be in the /Applications folder.
2. Follow the on-screen instructions to complete the Lion installation. Be sure you install Lion on the external storage device you've connected for this purpose, not your computer's boot drive.
3. When installation to your external device is complete, you can re-run Install Mac OS X Lion installer and upgrade the boot drive of your computer. A Recovery HD will likely not be created, but if you need to reinstall or repair your boot drive at a later date, you can connect the external drive you just prepared and hold cmd-r while restarting computer in order to boot from the external Recovery HD.

Please note that Recovery HD must be present on your computer's startup volume to use FileVault 2 (not an external Recovery HD).

Yes, you're missing the Recovery HD, that's why you can't turn on Filevault.

Do you have access to the App Store (through another machine), and if you click on Lion does it show that you have it installed/purchased already? If yes, you're in good shape (I've no idea what the status is in the app store if your machine came pre-installed with Lion).

You can re-download it from the App Store by holding the Option key and make a bootable USB stick. Either I or someone else can tell you how to do that (or you can search the forums, easy enough to find), but there's no point going that far till we know if you have access to App store or not.

Put the cursor on the Lion image (anyhwere in the square, try his nose for good measure), hold down the 'Option' key then click.

You should see the 'Installed' button change to 'Install', as in the pick. When it does, click 'Install'.

If you bought your MB Air with Lion already installed, it will not show up as a purchase in the App Store, so that line of investigation is of no use.

I'm a bit unclear on what is going on. I was under the impression that you couldn't even start up the machine, but then you're talking about going into the App Store. However, if you're getting a message that you need to reinstall Lion, that's probably what you need to do. First, make sure any data you have is backed up on an external hard drive (more than one, preferably) or some other device. Then, you need to enter recovery mode by holding down command-R. If you don't have a recovery partition, that's okay... your Mac will be capable of going into internet recovery mode. See:

http://support.apple.com/kb/HT4718

Once in recovery mode, you need to use Disk Utility to erase the hard drive. Then quit Disk Utility and reinstall the system, still while in recovery mode.

If that doesn't work, you should probably take the machine to your nearest Apple Store for assistance. (Be sure to make an appointment at the Genius Bar before going, don't just show up... they get busy, and may not be able to see you as a walk-in.)

• Open the Terminal, and type this command to list all partitions on your hard drive or SSD:
  diskutil list
  
• Look for 'Recovery HD' in the list, and note its identifier. It will be something of the form diskXsY, where X and Y are numeric digits.
• Type the following command to mount the recovery HD:
  diskutil mount readOnly /dev/[identifier]
  
• Replace [identifier] above with the identifier from step 2.
  
• The disk image inside the recovery HD is invisible, so use the Terminal to mount that too:
  hdiutil attach "/Volumes/Recovery HD/com.apple.recovery.boot/BaseSystem.dmg"
  
• Now, from the newly mounted Mac OS X Base System image, double-click the 'Install Mac OS X' application at the root of the disk. It launches, even when booted into a standard Mac OS X user account from the hard drive!
• Go through the license agreement. Once it asks you for a disk to install on, choose the external drive or spare partition.
• Enter your admin password when prompted, and the installer will start downloading.
• Open an old-style (non-autosaving) application that still uses the traditional Save, Save As..., etc. commands in the File menu and make a new unsaved document, and type a few things in it. This will give you a little insurance against the installer rebooting the system, since the app won't let the system reboot until you respond to its message asking whether you want to save the document or not.
• The installer will start downloading some packages into a folder called Mac OS X Install Data on the root of the drive you're installing onto. Of the files it puts in there, the interesting item is a package with a funky name. It will be the file in the folder with the largest file size. Once the file finishes downloading, the installer will extract the InstallESD.dmg image from it and delete the package. This will be fine as long as you don't let the app restart your machine.
• Once the installer finishes download and prompts you to restart your Mac, force-quit it. Do this quickly, as it may automatically reboot for you after a timeout period (although if you've got an unsaved document open, you should be able to prevent that).
• You should now have a file called InstallESD.dmg in the Mac OS X Install Data folder. You can burn this to a DVD, or image it to a USB flash drive to create a boot disk.

If you can get to the App store on your Air then you have a solution. As I understood your original post, you only get the support - 2002f error when you try to recover during cmd-R procedure right?

Forget that. If you can use your Air, go to the app store and Lion. Hold down the 'option' key and click the 'Installed' button. This will start downloading Lion Installer program for you (maybe you have to click it again to confirm, I forget). In any case, it'll take a while (45 minutes or so, I think, depending on your connection speed). You can either run the installer straight after its downloaded to reinstall Lion, or you can make a USB stick so you have a permanent external recovery drive (like I said, ask or search if you want to know how to do the latter).

OK, try that. Let us know how you get on.

If you click on the 'Purchases' tab in the top of the App store window, you should see that Lion is downloading. If it isn't, go do the option click thing again, make sure it changes to 'Install?'

(If I remember rightly there's two places where it says 'Installed', one under the name, and one over on the right hand side of the screen. Again, if memory serves, you have to press the correct one when you hold down the option key to re-download the installer but I can't remember which one it is. Try both, you can't do any harm here.)

EDIT: Another way to check: either in your dock or if you enter launchpad, you should see the Lion installer icon and an (empty) progress bar underneath it. This means its just started to download. Sit tight and wait. If the Lion installer icon isn't there at all, you haven't option-clicked the right button. Go back to the App store and try again.

If you bought your MB Air with Lion already installed, it will not show up as a purchase in the App Store, so that line of investigation is of no use.

Thomas, that was my impression, but the OP says it does show as installed. Read up a few posts.

Superflysamurai: Follow the advice in my post just before this one. I just confirmed this works on my Lion install.

Good luck!

Another way to do it, I just discoverd from Thomas' link.

Click on the purchases tab. After the purchases page loads, hold down the option key and click on the purchases tab again (yes, the same one at the top). This changes all your 'installed' purchases to 'install'.

Neat trick (I like that!).