November 14, 2012, 3:15 PM — Here's how you can download the Windows 8 ISO from Microsoft.
1. Visit the Windows Upgrade page on Microsoft's site.
2. Click the Install Windows 8 button.
3. Your file will begin to download.
4. Run the program on your computer.
5. Type in your Windows 8 product key.
For more, see the original article at the link below.
How to re-download the Windows 8 ISO | Ghacks