Microsoft has introduced Windows Experience Index (WEI) in Windows Vista, which help users to better understand how well Windows Vista and other software will perform on the PC. In Windows Vista, computer is rated with a “base score” ranges from 1.0 to 5.9 that is achieved by measuring the capability of computer’s hardware configuration. However, the WEI score in Vista has been dismal and surprisingly low for many, especially on gaming graphics card, causing overall rating to drop.

As such, Microsoft decides to change and tweak how Windows Experience Index works in Windows 7. In Engineering Windows 7 blog, Michael Fortin explained that:

The overall Windows Experience Index (WEI) is defined to be the lowest of the five top-level WEI subscores, where each subscore is computed using a set of rules and a suite of system assessment tests. The five areas scored in Windows 7 are the same as they were in Vista and include:

  • Processor
  • Memory (RAM)
  • Graphics (general desktop work)
  • Gaming Graphics (typically 3D)
  • Primary Hard Disk

Though the scoring areas are the same, the ranges have changed. In Vista, the WEI scores ranged from 1.0 to 5.9. In Windows 7, the range has been extended upward to 7.9. The scoring rules for devices have also changed from Vista to reflect experience and feedback comparing closely rated devices with differing quality of actual use (i.e. to make the rating more indicative of actual use.) We know during the beta some folks have noticed that the score changed (relative to Vista) for one or more components in their system and this tuning, which we will describe here, is responsible for the change.

For a given score range, we hope our customers will be able to utilize some general guidelines to help understand the experiences a particular PC can be expected to deliver well, relatively speaking. These Vista-era general guidelines for systems in the 1.0, 2.0, 3.0, 4.0 and 5.0 ranges still apply to Windows 7. But, as noted above, Windows 7 has added levels 6.0 and 7.0; meaning 7.9 is the maximum score possible. These new levels were designed to capture the rather substantial improvements we are seeing in key technologies as they enter the mainstream, such as solid state disks, multi-core processors, and higher end graphics adapters. Additionally, the amount of memory in a system is a determining factor.

Thus, Windows Experience Index will range from 1.0 to 7.9 in order to better measure faster graphic cards, multi-core processors and drives, such as solid-state drives. New tests and guidelines are been developed for each sub-components to get more accurate score.

Windows Experience Index base score in Windows 7 still take the lowest of five sub-scores, and not an average of all though, as the PC performance is usually determined by the speed of the slowest-performing component. To run Windows Aero, which is considered to be ‘must-have’ in modern computer, WEI score of at least 3.0 is required, while those with scores in the 4.0 to 5.0-range should be able to enjoy high-definition (HD) video and 3-D gaming.

Anyway, WEI is always a reference only, and users can easily hack to change the Windows Experience Index scores.