If you're currently running an older version of Windows and want to upgrade to Windows 8 when it's released, you might want to look at Amazon.com's upgrade deal.
A week of Windows 10, holograms and Exploding Kittens on Mars
Office 2016 launching this year, touch apps coming soon
Microsoft reveals the next version of Windows 10
Introducing Windows 10 for phones
Hands on with HoloLens
Download: Windows 10 build 9926