ExperienceIndexOK is a free portable tool which calculates and displays your Windows Experience Index, a benchmark which includes performance ratings for your CPU, RAM, graphics and hard drive.
This is particularly useful for Windows 8.1 and 10 users, as the previous WEI GUI (Control Panel > Performance Information and Tools) has been removed.
Launch the program and your current WEI rating is displayed for each system component.
Click "Re-run the assessment" to run the benchmark again.
Once it's finished, click ExperienceIndexOK > Screenshot... to save a screenshot of your results.
ExperienceIndexOK doesn't do very much - just runs the standard winsat executable and decodes the results - but that's still easier than doing it yourself, and if you miss the Windows Experience Index then this is a small and simple way to bring it back.