Not an MSDN subscriber? You can still download an evaluation version of Windows 8 RTM from TechNet.
This version provides a 90-day trial of Windows 8. Both 32-bit and 64-bit versions are available as ISO images in the following languages: Chinese (Simplified), Chinese (Traditional), English, English (UK), French, German, Italian, Japanese, Korean, Portuguese (Brazil), and Spanish. In order to use this evaluation, you must register and the product must be activated online with Microsoft-hosted activation and validation services.
Windows 8 works on the same hardware that powers Windows 7:
Processor: 1 gigahertz (GHz) or faster
RAM: 1 gigabyte (GB) (32-bit) or 2 GB (64-bit)
Hard disk space: 20 GB
Graphics card: Microsoft DirectX 9 graphics device with WDDM driver
Additional requirements to use certain features:
To use touch, you need a tablet or a monitor that supports multitouch.
To access the Windows Store and to download and run apps, you need an active Internet connection and a screen resolution of at least 1024 x 768.
To snap apps, you need a screen resolution of at least 1366 x 768.
Internet access (ISP fees might apply)
Download Windows 8 Trial
Scroll down and click on "Get Started Now" button. You may have to login with your Outlook ID and fill a small for downloading the ISO file.