Buy a Windows 7 PC and get Windows 8 Pro for $14.99.

Eligibility Details

The offer is for customers (e.g. Home users, students, and enthusiasts) who purchase a qualified PC. A qualified PC is a new PC purchased during the promotional period with a valid Windows 7 OEM Certificate of Authenticity and product key for, and preinstalled with:

Windows 7 Home Basic;
Windows 7 Home Premium;
Windows 7 Professional; or
Windows 7 Ultimate.
The promotional price is limited to one upgrade offer per qualified PC purchased, and a maximum limit of five upgrade offers per customer.

Key Dates

You must purchase a qualified Windows 7 PC between June 2, 2012 and January 31, 2013 to be eligible for this offer. The last day to register and order your Windows 8 upgrade is February 28, 2013.

Offer Redemption

Eligible customers must register for the Windows Upgrade Offer through this website by February 28, 2013.
After customer registration and Microsoft validation, customers will receive a registration confirmation email.
Beginning October 26, 2012, registered customers will receive an email with a promotion code and instructions for purchasing and downloading the software. The promotion code can be redeemed during the upgrade ordering process to receive the promotional price.

Customers will be able to purchase a downloadable version of Windows 8 Pro. An optional installation DVD is available for an additional fee, plus shipping and any applicable taxes or duties. Customers can also choose to create their own installation media on DVD or USB media after downloading Windows 8.
This offer requires internet connectivity for registering and ordering. Note: telephone or other access charges may apply

SOURCE