According to this article: http://blogs.msdn.com/ausdev/archive/2007/05/03/windows-vista-beta-2-rc1-and-rc2-set-to-expire.aspx
Those still running Beta and Release Candidate copies of Windows Vista are soon to be set to deal with their OS expiring.
This as a consequence means that people will either have to upgrade to the RTM version (which isn’t a bad idea) or find another alternative.
In the realm of commercial software development, this is a milestone in the lifecycle of an operating system. Community Technology Previews (CTPs), Betas and Release Candidates (RCs) form the basis of a mechanism for community inout into the development and growth of a platform while it is in flux.
The expiry of these early copies marks the maturity of the RTM product, and adds that final seal to the released version. A coming of age, perhaps.
While we are on the topic, I observed a number of emails to various technical mailing lists over the past few months painting Microsoft in a very unfair light – claiming that software vendors have not had significant time to adjust to the harsher requirements for running under Windows Vista’s new security model. When you consider how long some of these expirig Betas and RCs have been "in the wild" you have to question the validity of these wild claims.
The fact that previews were made available so early means that the company was truely looking to give vendors a head start, and since Vista only forces the implementation of the Windows XP Logo Certification model, it should be hardly a shock or suprise to many who make their bread and butter off the Microsoft technology platform.
Anyhow, I digress. Happy birthday Windows Vista. May your shell and explorer experience improve, like a fine red wine (over time).