Microsoft release Windows 8 Developer Preview edition &  can now download and install it. You can install it on a x86-based 32-bit or a 64-bit machine. Activation is not required. This is a pre beta version, you’ll want to install the OS on a spare PC or in a virtual environment so that it doesn’t interfere with your production or work machine.

System Requirements

Windows Developer Preview works great on the same hardware that powers Windows Vista and Windows 7:

• 1 gigahertz (GHz) or faster 32-bit (x86) or 64-bit (x64) processor
• 1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit)
• 16 GB available hard disk space (32-bit) or 20 GB (64-bit)
• DirectX 9 graphics device with WDDM 1.0 or higher driver
• Taking advantage of touch input requires a screen that supports multi-touch

How to install the Windows Developer Preview from an ISO image

The Windows Developer Preview is delivered as an .iso image that must be converted into installation media stored on a DVD or a USB flash drive. On Windows 7, the easiest way to convert this file is to use Windows Disc Image Burner. On Windows XP and Windows Vista, a third-party program is required to convert an .iso file into installable media—and DVD burning software often includes this capability.

Note: The .iso file that contains the developer tools requires a large capacity DVD called a DVD-9, as well as a DVD burner that can handle dual-layer (DL) DVDs. Most modern burners should be able to handle this format.