Microsoft just released the consumer preview for windows-8, that anybody can download and install on their computers.
For Windows 7 users, you can upgrade to windows-8. If you upgrade from XP, only your files and settings will be saved. [ You will have to re-install programs. ]
You can always install it in another partition, or in a virtual drive, for testing.
Here’s the download link, for both 32 and 64 bit versions.