Last night Microsoft released the public beta, or test version, of Windows Vista. You can download it or order it on DVD from here.
Microsoft warns that the software should not be used "in a production environment or on a main machine in the home". The site also says that once the software is installed you will not be able to "roll-back" to the previous operating system - you must either install the final Vista release or re-install an older version of Windows.
Vista is available in English, German and Japanese and in 32-bit or 64-bit versions. The Vista Team blog is here.®