If you update to Windows 10 Anniversary Edition you might find that you are now stuck at 30 FPS in CSGO (and probably other games).
The fix is to log in to the Xbox app (you will need an MS account - be sure to select the 'this app only' option when it's presented) then go to settings. Select the DVR tab at the top and switch it off.
In researching this I also discovered that the 30 FPS limit may also be caused by Nvidia's Shadowplay. So you may need to disable this too if you are running GeForce Experience.
this worked for me cheers oldie :yahoo: