Windows X's Live recommends:
Before and after making any changes to your system: Check Windows for registry errors.
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Service Pack 2 vested in Windows Vista and Server 2008 will soon be offered to all users via Windows Update. For the more impatient, it is already available as a package autonomous (or independent) with common installer to repatriate from the Microsoft Download Center

Like any service pack, SP2 this is no exception to the rule, namely that it includes all updates released since SP1. The advantage of a service pack is to facilitate the deployment of such updates and SP2 for this, we should not expect the contributions of his predecessor who had solved the many problems of compatibility and other recorded following the launch of Vist. 

Some improvements, however:

• Compatibility with 64-bit CPU VIA Technologies
• Windows Vista Feature Pack for Wireless: Support Bluetooth v2.1, Wi-Fi setup Windows Connect Now
• Improve the performance of Wi-Fi connections after waking the
• Updates RSS component
• Ability to record data on a Blu-Ray
• Windows Search 4.0 for local search
• Improving the operation of Windows Media Center (content protection for television)
• Adding a registry key to changing the maximum number of open TCP connections 

More information's and download page you can find here.