Windows Vista Service Pack 2 is the final version of the second update package for Vista users.
The service pack contains all the Vista updates released by Microsoft since Windows Vista Service Pack 1. These updates fix system problems and vulnerabilities. Service Pack 2 enhances wireless and Bluetooth connectivity, and also features an updated versions of Windows Search 4.0, which again improves the comparably weak Windows search
To run Service Pack 2, you have to have Service Pack 1 installed already. Also remember that if you installed the release candidate, you'll need to uninstall it before installing this final version.
With general system improvements and fixed vulnerabilities, Windows Vista Service Pack 2 is a must-have for all Windows Vista users.