Looking back, Vista has been available for 18 months if you take in to account the original public beta release back in Summer 2006. However, it hasn't been as popular as Microsoft anticipated. Why not? The problem is that the majority of software has to be upgraded, which means that corporates will need multi-workstation licenses, which results in huge expense. Also, Vista isn't particularly fast compared to XP, which means that if you have an old PC, you might see a performance hit.
So, Microsoft have been busy working on the first Service Pack and the release candidate has been made available as a public download. Although officially it won't be available until early 2008, you can get the benefits of a new release - including some new features - right now.
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