Remember the Windows Experience Index? It was first introduced in Windows Vista to showcase a PC's performance via a number. Measuring the hard drive, memory, processor, graphics card, and gaming performance, the Experience Index would tell you how well your PC would perform.
With the introduction of Windows 8.1 Preview, it appears that Microsoft has changed directions when it comes to the Windows Experience Index, as it is no longer available. When you visit the System option in the Control Panel, you will notice that a score is no longer available nor can you install or enable the Windows Experience Index.
"In theory, it was supposed to make it easy for the consumer to know if a software or game would run on their PC. For example, if a software required the PC to have a base score of 4.6 but the PC had a base score of 3.1, the user would know that the software might not be a good purchase for their PC," Mcakin's mentions.
For those most part, software system requirements weren't affected by the Windows Experience Index. Perhaps we will see its return in the final version of Windows 8.1, but we doubt it. More on this as we get word from Microsoft.