Windows 8 trial version is available and free to download. However make sure that you have backed up your data as in trial version due to glitches systems may crash.
If you install Windows 8 Consumer Preview using the Windows 8 Consumer Preview Setup program, you won't need to enter a product key—the setup program automatically provides the product key.
Windows 8 Consumer Preview could not be uninstalled once you install it in your PC or laptop therefore if you need to revert back to Windows 7 or Windows Vista then you must reinstall it from the recovery or a fresh installation so one must backup the data before installing Windows 8 Consumer Preview.
Windows 8 Licence Key
If you create installation media, start your PC from the media, and then install Windows 8 Consumer Preview. You'll need to enter this product key: DNJXJ-7XBW8-2378T-X22TX-BKG7J.
Do not try if you are a business personnel and with the stable windows version and if you are a developer and you know what you are doing – please go ahead try it and leave the feedback for millions to get benefitted.