I have MS Dual Core Hotfix installed....and i did the thing in registry which i have to do ... but still i am getting the stutters when running Need for Speed Most Wanted....
How much RAM do you have on that machine? Also, what about HDD. These things attribute to overall machine performance. If you don't have enough RAM, that will certainly cause problems.
You can disable cool&quiet in your bios. Also, try setting the affinity like Mike said. You can also try adding the /usepmtimer parameter to the end of the boot line in the boot.ini file.