If you have any beta versions of SP2 installed, they must be uninstalled prior to installing the final version. To do this, use the Control Panel applet called Programs and Features, select View installed updates, and then under Windows look for KB948465. SP2's main requirement (assuming no incompatible drivers are detected) is that SP1 is already installed. During the beta phase, it was speculated that this is because SP2 is not yet finalized, but the truth is that SP1 is a prerequisite even now.
The reason for this is size: Microsoft wants the size of SP2 to be smaller (if SP2 was cumulative, it would make for a huge download). Server 2008 shipped with SP1 already installed (meaning SP2 is actually the first service pack for Server 2008), including the contents of the SP1 client code.
SP2 applies to both the client and server versions of Windows because Microsoft adopted a single serviceability model to minimize deployment. Also, by releasing one single service pack, Microsoft has less testing to do, since Vista and Server 2008 have the same binaries for all common files, making for a quicker release (SP1 was released 14 months ago).
There are a few significant additions that are included in SP2: Windows Search 4.0, Bluetooth 2.1 Feature Pack, the ability to record data on to Blu-Ray media natively in Vista, Windows Connect Now (WCN) is now in the Wi-Fi Configuration, and exFAT file system supports UTC timestamps. The service pack contains about 800 hotfixes. For those interested in a more complete changelog, I've included one below:
- Hardware ecosystem support and enhancements
- SP2 adds support for the 64-bit central processing unit (CPU) from VIA Technologies, which adds the ID and vendor strings for the new VIA 64-bit CPU.
- SP2 integrates the Windows Vista Feature Pack for Wireless, which contains support for Bluetooth v2.1 and Windows Connect Now (WCN) Wi-Fi Configuration. Bluetooth v2.1 is the most recent specification for Bluetooth wireless technology.
- SP2 improves performance for Wi-Fi connections after resuming from sleep mode.
- SP2 includes updates to the RSS feeds sidebar for improved performance and responsiveness.
- SP2 includes ability to record data to Blu-Ray Disc media.
- Operating system experience updates
- SP2 includes Windows Search 4.0, which builds on Microsoft’s search technology with improved indexing and search relevance. It also helps find and preview documents, e-mail (including signed e-mail messages), music files, photos, and other items on the computer. The search engine in Windows Search 4.0 is a Microsoft Windows® service that is also used by programs such as Microsoft Office Outlook® 2007 and Microsoft Office OneNote® 2007. Autotuning Diagnostics in SP2 now interprets current network conditions when implementing Windows scaling. This feature includes full netsh support.
- SP2 improves Windows Media Center (WMC) in the area of content protection for TV.
- SP2 removes the limit of 10 half open outbound TCP connections. By default, SP2 has no limit on the number of half open outbound TCP connections.
- Enterprise improvements
- SP2 provides the Hyper-V virtualization environment as a fully integrated feature of Windows Server 2008, including one free instance with Windows Server 2008 Standard, four free instances with Windows Server 2008 Enterprise and an unlimited number of free instances with Windows Server 2008 Datacenter.
- SP2 increases the authentication options for WebDAV redirector, enabling Microsoft Office users greater flexibility when authenticating custom applications using the WebDAV redirector.
- SP2 provides an improved power management (both on the server and the desktop), which includes the ability to manage these settings via Group Policy.
- SP2 improves backwards compatibility for Terminal Server license keys. Windows Server 2008 changed the licensing key from 512 bytes to 2,048 bytes which caused clients using older Terminal Server versions to fail. SP2 allows legacy license keys on Citrix applications to work with Windows Server 2008 Terminal Server.
- Setup and deployment improvements
- Provides a single installer for both Windows Vista and Windows Server 2008.
- Includes the ability to detect an incompatible driver and either block service pack installation or warn users of any potential loss of functionality.
- Provides better error handling and descriptive error messages where possible.
- Improves manageability through logging in the system event log.
- Provides a secure install experience.
- Includes the ability to service the installer post release.