[HOW-TO]: Fix "This device isn’t eligible for the requested build" Problem

I have this problem when I tried to upgrade my iPad 1 to iOS 5.0.1. Each time I tried I got the following message: “The iPad "your_ipad_name" could not be restored . This device isn’t eligible for the requested build.“

Thankfully the solution is simple and falls into one of two areas:

1. The iOS version that’s been downloaded isn’t the right one for the device.
2. There’s an entry in your host file redirecting Apple traffic to another location.

In most cases, it’ll be the second option.

Mac OS X

1. On your Mac, open your Applications folder.

2. Navigate to the Utilities folder.

3. Open Terminal.

4. Type “sudo nano /etc/hosts” (without quotes) and press enter.

5. Enter your password

6. Use the down arrow key to find the gs.apple.com entries. Once the cursor is in front, make sure you comment out the line(s) by entering # in front of the text.

7. Save the file by pressing CONTROL+O.

8. Exit the nano editor by pressing CONTROL+X.

9. Restore your iDevice.

Windows

1. Press Start, then Programs, then Accessories

2. Launch Notepad or WordPad

3. Click Open from File menu.

4. Browse to Windows/System32/drivers/etc

5. In “files of type:” select all documents

6. Open “hosts”

7. Delete all line that have gs.apple.com or similar

8. Hit Save

9. Restore your device

You should now be sorted and up and running! Please feel free to share your experiences in the comments section below.