<posted by Apple Certified Tech>
Step 1: Obtain Micro USB (if you don't have one). If you are not SURE, check here:
http://en.wikipedia.org/wiki/File:Usb_connectors.JPG
Step 2: Download the .ipsw file. Make sure it STAYS an ipsw file. Don't rename.
http://www.megaupload.com/?d=9RRLTLBU
Step 3: Drop the .ipsw file into this folder (mac), orequivalent on PC. Delete any old filesin this folder:
Users/UserName/Library/iTunes/Apple TV Software Updates
Step 4: With iTunes open, connect Apple TV to computer viamicro USB. NO POWER CABLE, or HDMI.
Step 5: Your Apple TV should appear in iTunes. Click “restore”. iTunes will look in that folder and see your.ipsw file and you are done.
ALTERNATELY, you can hold down option when clicking restoreand it will ask you to manually identify the .ipsw file. I did the way listed 1st, and itworked without any issue on the first try.
Good luck!