If you want to play with the latest Microsoft Vista build, it's available to
the public here.
This page includes information to help you download a special test build
of Windows Vista. This build (5728) has a number of improvements and updates
from RC1, but has not been put through the same internal testing process as
RC1 and therefore may be unstable in certain installations. We are making this
release available for a limited time only (and only by download) in order to
get broad distribution and testing in a variety of PC configurations.