Microsoft has put the beta 2 release of Windows Vista up for free download in three languages (English, German, and Japanese) and in both 32-bit and 64-bit editions. The drawback: it's a 3.5GB download, though you can order it on DVD. Also it comes with the usual beta warning:
Note: This is beta code and should not be used in a production environment or on a main machine in the home. Beta 2 is intended for developers, IT professionals and technology experts to continue or begin their testing of Windows Vista. Before you decide to use Beta 2, you should feel comfortable with installing operating systems, updating drivers, and general PC troubleshooting. Some risks of using beta operating systems include hardware and software incompatibility and system instability. If you have concerns about installing this beta software on your computer, we encourage you to obtain the final release version of Windows Vista when it is available in 2007.
Basically, you get to use Vista free for a year, before it expires. After that, you have to buy a copy.
You can install Vista as an upgrade to Windows XP, but there is no uninstallation procedure. If you install it, that's it. The only way out is to do a clean installation of XP. For this reason, it's better to install it on a different disk partition.
