Microsoft have today, released a document at their Download Center, that describes the changes in functionality for Windows XP Professional x64 Edition over Windows XP Professional SP2.
Overview
The document provides information regarding features that differ in functionality from Windows XP SP2. It is important to note that the document uses the Windows XP SP2 feature set as the baseline for comparison with Windows XP Professional x64 Edition. Features not documented here are at parity with Windows XP SP2 and function the same way.A Genuine Microsoft Software check is required, in order to download the document.
View: Changes to Functionality in Microsoft Windows XP Professional x64 Edition - English

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