Service Pack 2 is fundamentally different from anything Microsoft has ever done. Like any service pack, it contains a roll-up of all the bug fixes and security patches that Microsoft has released since Service Pack 1, which was about a year ago. But the big thing about SP2 is that to a considerable extent, it replaces the existing security model of Windows XP. It changes a great number of installation defaults to a much more secure configuration, which isn't hard considering that the default configuration of XP is essentially hopeless. And it changes a number of security internals to get what Microsoft promises will be a much more secure computing environment than we have ever had with a Microsoft desktop operating system. Within the enterprise, deploying it won't be too bad because it's managed. Use SMS or whatever and you can deploy what you want and set your defaults according to policy. Where it's really going to be an issue is when people start deploying it on their own machines that are occasionally connected to your networks. For one thing, it's going to break applications. They're trying to keep that to a minimum but applications that operate at a very low level, especially those that integrate with the security system -- leading candidates being anti-virus software and virtual private networks -- are likely to break.