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Game performance may be poor on a Windows XP-based computer that is using a dual-core processor especially on AMD dual-core computers.

If you have the following, then download the fix at the bottom of this post:

• Microsoft Windows XP Service Pack 2 (SP2)-based computer.
  
• The Windows XP SP2-based computer has multiple processors.
  
• The multiple processors support processor power management features. For example, the multiple processors support Advanced Configuration and Power Interface (ACPI) processor performance states.
  
• The Windows XP SP2-based computer requires Windows XP SP2 to use the processor power management features.

Download fix: here
More info: here