After years of development and several postponements, Microsoft on Wednesday opened Windows Vista to public beta testing.

Wednesday afternoon, Microsoft made available English-, German-, and Japanese-language versions of Vista, each in either 32- or 64-bit editions, for downloading. The files, which are in .iso format, are extremely large: the English language, 32-bit version, for example, weighed in at 3.13GB.

Once downloaded, the file must be burned to a DVD. Users not equipped with a DVD-RW drive can order a physical disc for a small fee; U.S. users, for instance, will pay $6 for the disc, plus another $4 shipping and handling.

Product registration keys, which are required to install Vista from the DVD, will be e-mailed to those who download Beta 2 -- officially called the Customer Preview Program (CPP) -- and included with discs mailed to users.

To help users manage the download -- particularly to pick it up if the connection's lost -- Microsoft's partnered with Akamai Technologies, which provided a download management utility. Internet Explorer users download the manager as an ActiveX control; users of other browsers, such as Mozilla's Firefox, are provided a Java version of the utility.

The starting point for downloads or ordering is this page on the Vista Web site.