Reliability
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Improved reliability when working with external displays on a laptop.
Improved Windows Vista reliability in networking configuration scenarios.
Improved reliability of systems that were upgraded from Windows XP to Windows Vista.
Increased compatibility with many printer drivers.
Increased reliability and performance of Windows Vista when entering sleep and resuming from sleep.
Performance
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Improves the time to become active from Hibernate and Resume modes.
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Improves performance of Windows® Internet Explorer® 7 in Windows Vista, reducing CPU utilization and speeding JavaScript parsing.
Improves battery life by reducing CPU utilization by not redrawing the screen as frequently, on certain computers.
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Addresses an issue in the current version of Windows Vista that makes browsing network file shares consume significant bandwidth and not perform as fast as expected.
WHO HOO!!!