The Windows Experience Index measures the capability of your computer's hardware and software configuration and expresses this measurement as a number called a base score. A higher base score generally means that your computer will perform better and faster than a computer with a lower base score, especially when performing more advanced and resource-intensive tasks.
Each hardware component receives an individual subscore. Your computer's base score is determined by the lowest subscore. For example, if the lowest subscore of an individual hardware component is 2.6, then the base score is 2.6. The base score is not an average of the combined subscores. For more information about WEI, see: Engineering Windows 7 : Engineering the Windows 7 "Windows Experience Index"
This will show you how to update or refresh the Windows Experience Index (WEI) score in Windows 7
to help measure the capability of your computer.