In an effort to move people away from the dying Windows XP, Microsoft is running a new promotion in North America for those who ditch their Windows XP PC and buy a new PC with Windows 8. There are some restrictions though, you have to trade in your computer at a Microsoft Store and the rebate is only valid for Windows 8.1 PCs that cost $599 or more.
You can find the details of this action at the Microsoft Store.
The caveat is that you have to trade in your computer at a Microsoft Store, and you have to buy a new Windows 8.1 machine that costs $599 USD or more (limiting the maximum discount is roughly 16 percent).
The good news is that most of the laptops and desktops at Microsoft stores are relatively new, so it's unlikely that Amazon.com, Inc. (AMZN), Newegg, and other online retailers will be able to offer a better deal, on average.