The problem you're describing is quite routine for faster newer computers when using a sound board as the joystick port.
Unchecking Poll with Interupts is Microsoft's patch fix for this problem, but in the long run it's not the greatest fix. You should do that first just to see if you can get back to playing the game.
This well documented problem is due to using a soundcard joystick port. The card is being asked to do too much at these speeds and eventually they all overheat and your spiking will get worse. The best solution is to use one of the new USB sticks. The next best solution is to buy a new stand alone game port board such as the PDPI l4 or Thrustmaster etc. These are either lighting fast or have small adjusters to match the speed of your new cpu. They will have detailed instructions on how to disable the soundboard game port so you can choose them during set up.
You indicated that this just started with your new cpu and connection to your sound board so don't start taking the stick apart yet. You can read about this at the Thrustmaster site as well as the PDPI l4 site.
Personally, If I were going to spend up to $50 or $60 dollars for a new gameport board, I would put that towards a new Saitek combination that includes both a good throttle and stick for $100 that will plug into your USB and be rock solid. You will get as many combination of buttons as a Thrustmaster tqs with Pro stick. The're sold at Comp USA. Then, like me, when CH comes out with good USB stuff you can switch to them and have a great backup stick.
Ranger Bob