Microsoft Windows 8 Pro or Windows 8 Pro Pack (pre-order) + $30 Amazon Promotional Credit $70

Amazon has Microsoft Windows 8 Pro or Microsoft Windows 8 Pro Pack for $39.99 after $30 Amazon Credit + Free Shipping! (This is for Physical Disc - Limited Time Offer)

Microsoft Windows 8 Pro: Link [amazon.com]

Microsoft Windows 8 Pro Pack: Link [amazon.com]

If your PC is running Windows 8 Pro and you'd like to get Windows 8 Media Center Pack so you can watch and record live TV with Windows Media Center, you can take advantage of a limited time special offer and get Windows 8 Media Center Pack for free!

You can add Windows Media Center to Windows 8 Pro For Free: Link [microsoft.com]

Also if you like to buy Windows 8 Pro for clean install or for a system with No Operating System, Amazon have $30 off promotion code for a limited time:

For a limited time save an additional $30 on Windows 8 64-bit System Builder Software. Simply enter the promotional code WIN8SYST on the Review Order page and the discount will be applied at checkout. Promotional code limited to one per customer. While supplies last, applies only to products sold by Amazon.com and not third party. Offer valid October 19, 2012 through October 25, 2012, subject to change.

Windows 8 Professional System Builder DVD 64-Bit : Link [amazon.com]

Note:

Pre-order Select Windows 8 Software, Get a $30 Amazon.com Promotional Credit Through October 20, 2012, purchase select Windows 8 software and get a $30 Amazon.com promotional credit toward the purchase of items shipped and sold by Amazon.com (certain exclusions apply, including Kindle books, MP3s, and video rentals and downloads). The promotional credit will be emailed thirty days after your order ships. Offer valid when shipped and sold by Amazon.com. See full terms and conditions for more details.

Update (New Amazon Offer):

Through October 27, 2012, purchase select Windows 8 software and get a $30 Amazon.com promotional credit toward the purchase of items shipped and sold by Amazon.com (certain exclusions apply, including Kindle books, MP3s, and video rentals and downloads). The promotional credit will be emailed thirty days after your order ships. Offer valid when shipped and sold by Amazon.com. See full terms and conditions for more details.


Frequently Asked Questions:

Can I upgrade from a Windows operating system older than Windows XP?
If you want to upgrade from an earlier Windows operating system than Windows XP (for example, Windows 95 or Windows 2000), you'll need to purchase the Windows 8 System Builder. You won’t be able to keep any files, settings, or software programs when you install the new operating system.

Can I upgrade from a 32-bit version of Windows to a 64-bit version of Windows 8?
If your PC has a 64 bit-capable processor (CPU) but is currently running a 32-bit version of Windows, you can install a 64-bit version of Windows 8. You also won't be able to keep any files, settings, or software programs when you upgrade from a 32-bit to a 64-bit version.

If I upgrade and select "keep nothing," how can I restore my files after the upgrade?
If you're running Windows Developer Preview or Windows 8 Consumer Preview when you upgrade, or if you choose the option to "keep nothing" when you upgrade, your files won't come with you to Windows 8. However, you might still be able to copy your files over after you upgrade. If you don't reformat your hard drive during installation, your files are saved to the Windows.old folder, where you can retrieve them after the upgrade.

If I change my mind, can I uninstall Windows 8 and go back to a previous version of Windows?
Not exactly - To go back to your previous version of Windows, you'll need to format your hard drive and then reinstall the previous version of Windows from the recovery or installation media that came with your PC. Typically, this is on a DVD. If you don’t have recovery media, you might be able to create it from a recovery partition on your PC using software provided by your PC manufacturer. Check the support section of your PC manufacturer’s website for more info. After you install Windows 8, you won’t be able to use the recovery partition on your PC to go back to your previous version of Windows.

How can I tell if my devices (keyboards, mice, webcams) will work with Windows 8?
Windows 8 generally works with the same peripheral devices and apps that work with Windows 7. In some cases, a device or program might require an update. The best way to tell if your devices will work before you upgrade is to run Windows 8 Upgrade Assistant, a free program that scans your current hardware, software programs, and devices for compatibility.

Can I upgrade my PC currently running Windows 7, Windows XP, Windows Vista, Windows 95, or Windows 2000 to Windows 8 using the Windows 8 Pro Pack product?
No. You’ll need to purchase the Windows 8 Pro (Professional) product. The Windows 8 Pro-Pack product let’s you upgrade only if you have a device already running Windows 8 ("Core") operating system.

Update! Windows 8 Features:

Lot of misconception and many misleading information from people in this thread (Both positive and negative). I recommend you to spend some time and get information you like to know about Windows 8 from valid sources.

Building Windows 8 Blog (MSDN) is a very good and valid source to get your information about Windows 8 and new features that are coming with Windows 8: Link [msdn.com]

And Microsoft Windows Team Blog is a good source to get a valid and correct information about Windows in general: Link [windows.com]