Run the Atto bench mark as posted above by BigJimmy and see what results you get.
Windows Experience Index isn't the be-all and end-all in all honesty, I wouldn't take what it says as being 100% accurate, althought in this case it may well be pointing to something wrong in the set up somewhere, but run Atto to be sure and post the results.
Edit: is this a clean install on a new drive? if you have installed windows on the drive more than once did you secure erase the drive prior to the last install?