The Windows Experience Index is a very basic benchmarking tool that measures your system's performance. Microsoft removed the Windows Experience Index in Windows 8.1, but WEI Tool brings it back, just like you remembered it.
While the Windows Experience Index was never perfect, it was a useful quick way to find bottlenecks on your PC, since it will show you if one component is drastically older or slower than the others.
WEI Tool is almost identical to the original tool: just start it up, run the scan, and it will give you the results in a small window. It also provides buttons to take a screenshot, upload it to Imgur, or save your results as an HTML file. Plus it's portable, so you don't have to install anything.
Check out the video above to see it in action, or download it at the link below.