Microsoft has unveiled its Windows 8 over at their Microsoft Build event, and has also made available their Windows 8 Developer preview. It’s now available for download over at Microsoft’s page. This is what the Windows President has to say about the preview:

You probably want to try out the preview release—and you can. Starting later tonight you can download the Windows 8 Developer Preview. This includes a 64-bit (x64) build with development tools to build apps, and a 32-bit (x86) or 64-bit (x64) build without development tools. The releases also include a suite of sample applications (please note these are merely illustrations of potential apps, not apps that we intend to ship with Windows 8). The ISOs are linked to from http://dev.windows.com.

Upgrade from Windows 7 installation is not supported for pre-release code; only clean installs are supported. Reminder: this is a developer preview release and is not meant for production. It is not a beta release. We will be updating the release with various quality updates and drivers over the coming weeks/months just to exercise our overall update and telemetry mechanisms.