The Windows Experience Index rating and the WinSAT command do not work correctly on a Windows Vista-based or Windows Server 2008-based computer that has more than 8 logical processors
When you are running Windows Vista or Windows Server 2008 on a computer that has more than 8 logical processors, the Windows Experience Index rating is unavailable in the system properties. Additionally, when you run the WinSAT command (Winsat.exe), the command exits with a fatal error message. For example, you receive the following error message when you run a WinSAT CPU -Encryption command:
Error: The WinSAT XML does not adhere to the schema.
This problem occurs on a computer that has more than 8 logical processors. For example, you have a computer that has two quad-core processors and hyper-threading is enabled for these processors. In this example, you have 16 logical processors because hyper-threading makes each core appear as two logical processors to the operating system.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB967191.