The Windows 8 Preview is being offered in three different packages–a 64-bit version with various developer tools, a 64-bit version of just the operating system, and a 32-bit version of the OS.

Download Windows 8 Pre-Beta ISO

• Windows 8 Developer 32-bit (x86) [2.8 GB ]
• Windows 8 Developer Preview 64-bit (x64) [3.6 GB]
• Windows 8 Developer Preview with developer tools English, 64-bit (x64) [4.8 GB]

Windows 8 Developer Preview Product Key

If Windows 8 Developer Preview installation failed during first attempt or if you’re planning to use Reset your PC setting on Windows 8 or reinstall Windows using installation disk, you should know: you need to enter Windows 8 Developer Preview Product key during installation as the setup asks you.

A forum thread at the Microsoft Developer Network forum has the answer. A user is asking Microsoft there about the product key that needs to be entered during reinstallation of Windows 8.

Microsoft responds with the following answer:
If you need to reinstall Windows Developer Preview or use the Reset functionality, you might be asked to enter this product key:

6RH4V-HNTWC-JQKG8-RFR3R-36498

If you’re running a server version of Windows Developer Preview, you can use this product key:

4Y8N3-H7MMW-C76VJ-YD3XV-MBDKV

Note: These product keys are only for use with the Windows Developer Preview version of Windows 8.